nwflyboy: Sorry, I saw this thread kind of late; haven't been checking in as much since SB was down for a while. A search should turn up my old trip report from 2005 - I think I just had Sint Maarten in the title
(edit - found it, here it is:
http://www.scubaboard.com/showpost.php?p=1171555&postcount=1 )
I'd second DiverDonn's suggestions, but perhaps with a little more time at St. Maarten. There is fun to be had just driving around the island, seeing the different towns (I was especially fond of Marigot, and yacht-sightseeing in Grand Case), and I found I really needed non-diving days to dry out, especially for the last couple of days before the flight home. Phillipsburg itself is kind of plasticized, not to mention mercenary....the shopkeepers are all trained by the cruise ship passengers too well, unfortunately. Anyway, if you consider yourselves still a bit 'intermediate/beginner level' then a few dives on St. Maarten might be just the ticket before moving on to Saba. I won't say the diving is great - in fact, looking back on it now I've been to the Flower Gardens off the Texas coast, I'd have to say it was kind of bleak by comparison. BUT the Dive Safari's shark dive was really good...not one of the 'chum the water and drive them nuts with a huge fish-sicle' dives, but got you good and close to a few reef sharks just the same.
Planning a couple extra days in SXM, it's also worth it to consider a ferry from Marigot over to Anguilla. I didn't scuba there, but I still think Shoal Bay is one of the most beautiful sights I've ever seen, and there is some snorkeling to be had right there. I don't think the ferry was more than $30 round trip, probably less, and not a long ride. And it was not crowded by any means, at least when we went in July.
DiverDonn's got the airfare to Saba right too if I recall - it was between $100 - 200 round trip, depending on what deals you got, and the plane is low enough that you can still dive the last day...just do the 2 morning dives, skip the afternoon dive, and take the last flight out and you should be fine.
I'd strongly recommend SabaDeep for scuba there. The other ops are great I'm sure, but SabaDeep is small and very, very personal. Not only is it not a cattleboat, you can pretty much expect the person driving the boat will be your dive leader too. And Sally does a great lunch in their restaurant between dives 2 and 3, rather than just eating out of a cooler on the boat. We also got to dive with one of the locals (e.g. JoBean who's a glass artist, has a shop near El Momo cottages) as she goes out with them. I considered that an endorsement, but that was our last dive there so we didn't need convincing by that point. Diving in Saba is considered 'challenging' because of the depths involved - your first dive of the day WILL be over 100', generally over 110'. In retrospect my wife and I might've been doing Saba "too early" in our careers experience-wise, but we seemed to do fine, so its up to you how comfortable you are as an intermediate/beginner. I will say I never felt current there anywhere near like what I've since dealt with in the Flower Gardens on occasions, and having a guide with you makes a big difference - the dives are all lead, and are not time-managed except basically by the first person hitting half-pressure (1500). Computers definitely recommended vs. tables.
10 days was almost exactly our itinerary. We stayed in a vacation rental/condo type place in the Dutch Lowlands - Summit Resort, nicely quiet and out of the way, with a fun little bar by the pool to relax after the day's adventures and have a final drink or two) and actually paid to keep the room while we were in Saba for 2 overnights too (I know, sounds wasteful, but that way we only schlepped what we needed to over on the small flight, and had a nice home base to return to after a couple days without air conditioning in El Momo Cottages on Saba. If you prefer more 'comfort' then I've heard the Princess Juliana resort or the Gatehouse in Saba are the recommended places to stay. I've also heard of the Willard's place, but hear about the others more. Not knocking El Momo, but since we were diving all day we do wish we picked someplace with actual hot showers (not just solar) and AC.
I don't have any insight on Statia at all, unfortunately, aside from a divemaster on a Windjammer we took long ago talking about that being the place to go sand-sifting on your dives for the 'slave beads' that used to be used as surrogate money for what little the slaves were permitted to purchase. Kind of a sad historic thing, I suppose. I did find a tiny fragment of what we thought to be old Delft pottery in the sand at Anguilla, but there's no way of proving provenance so for all I know it could've been in the water less than a year. ;-) Made a nice little centerpiece on a shell necklace I made.

Sorry, I'm rambling.
To sum up, sounds like you're getting good advice from DiverDonn and hopefully my trip can help as well. My vote would be to spend a full two days in SXM diving 2 tank dives and use the evenings for dinners and a little sightseeing, get your 'feet wet' so to speak, then go over to Saba to dive 3-4 days there. My vote would be for 3 dives each day, but if you want to hike Mt Scenery (or anywhere, frankly - that island is STEEP) you will definitely NOT want to do that on 3-dive days or you're both into 'elevation' concerns as well as kicking your own heiney exhaustion-wise. That gives you time after getting back to take a day-trip over to Anguilla for just plain beach relaxing, and still drive around SXM and do more dry-trip stuff. That way all your wetsuits et al have time to dry out before you pack up for the trip home.
Substituting Statia for some of the time in SXM might not be a bad idea, either, but I can't give advice on that front.
Let us know how it works out, please!!!
And since I see you're coming in from the west coast, I know you've already got the trip booked, but did you consider the Sea of Cortez along Baja Sur at all, or have you already done that? I ask partly because I'm considering Loreto for one of my next trips (I've got a brother in Portland, so that would be a place we could both get for about the same travel time and $$ to go diving).
Anyway, PM me on that front if you've got any info...don't want to hijack this thread.