I agree with Damselfish in that most quality back infated bc's have trim pockets that accomplish the same thing as a bp.
I know that nearly everyone here that has a BP/W really loves them. Me included. But just because it's right for me doesn't mean it's right for you. It's hard to tell you what to buy because allot of it really is personnal preference.
Here's what I like about my BP/W.
It really locks the tank to your body. Much more secure than any BC I've owned.
Easier to get in than my Zeagle. Getting out is about the same.
I don't have to carry near as much weight to the boat (let alone when diving). Most people don't realize their BC weighs about the same as a BP/W, but is also bouyant, so you'll need more weight just to get your BC neutral. Not a big thing, but the little things add up. With a steel tank and a shorty, I don't need any additional weight. And that's without an STA.
Packs much better than my Zeagle Brigade.
Others will tell you it's more streamlined, and I'm sure they are right, but that isn't an issue for me. I'm not a DIR type diver.
Things I like better about my Zeagle: Pockets
So you have $400 to spend. Here's my set up.
DSS adjustable harness (bought it used for $70).
http://deepseasupply.com/
You could also get the Oxycheq
Adjustable Harness System
http://www.oxycheq.com/Wing_Access.html
You can also get this from Scubatoys, but it's not on their website.
SS HammerHead Back Plate with Heavy $100
http://www.hammerheadscuba.com/hh2.htm
Oxycheq 30# Signature wing $258 (I think - There's a 10% savings for being a scubabord member) from ScubaToys.com
http://www.scubatoys.com/store/detail.asp?product_id=OXYSSWing
You can save a little by going with the standard series wing
http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=OXYStdWing
Apex Weight Pockets $110
So, if you get the the Oxycheq harness & wing from Scubatoys, along with the backplate from Hammerhead, you'd be close to your $400 budget. You can get by with less expensive weight pockets, or use a weight belt if needed.
Oops, I almost forgot. You'll have to have 2 tank cam straps. I got mine for $18 each from my LDS. I know Scubatoys has these also.
If you like the Dive Rite setup, you can get the complete setup from Dive Sports. Just ask for Phil.
http://www.divesports.com/IndexPages_Brand/diverite_brand.htm
Even though it's not on the web site, I think you can get a transplate system with Rec wing & weight pockets for just about $500. Plus he'll include shipping for free, and set the whole thing up.
I think Scubatoys also sells dive rite, so pick which ever vendor you like best. (I like ScubaToys a little better, but I've bought from both.)
Having said all that (I think this is by far my longest post), the best thing is to try as many setups as you can, then buy what you really want within your budget.