After much personal research, I just bought GEOs for my wife and I. We did just two dives with them last week and they worked as they were supposed to.
LeisurePro has the old style Geo listed on their web site for $275. Here's a suggestion - CALL them and ask them if they have those in stock. If they do not, ask them if they will sell you the new style at that price.
They might do it (I'm speaking from my recent experience) so it's worth a try. Be aware of the colors available. If you order new style blue thinking it'll be black with a blue face like the old style, it will not be. The new style blue one is all blue and white. Look at the other new style colors available and be ready to specify what you want before you call.
Otherwise, if they do have the old style GEOs in stock, all of the functions on those are the same as the new style ones, so if you don't mind the way they look you could buy those. Only the bands and colors (cosmetic stuff) are different between the old and new style GEO. You could also just go with the new ones at full price (since you mentioned your budget is $500 each).
Old Style:
http://www.leisurepro.com/Prod/OCNGE...3don&Hit=1
See both old style colors on Amazon (Leisure Pro's ad there)
http://www.amazon.com/Oceanic-GEO-Wr...9480844&sr=8-1
You can download the manual and also a nice safety reference manual from Oceanic and study them before you buy. They will tell you about the algorrythm used.
http://oceanicworldwide.com/pdf/12-2734-r02.pdf
http://oceanicworldwide.com/pdf/12-2262-r10.pdf
Ours came with lens protectors (removable clear plastic cover to protect the lens from scratches), battery cover removal tools, and wrist band extensions in the box. That was a nice surprise, I almost ordered all those things separately.
I like the GEO a lot. Except for air integration and a compass, they have basically the same functions as all Oceanic computers (according to a chart in the Oceanic catalog, also available from their web site) The free Oceanlog software is okay (if you chose to download your info to your PC). It's neat to see a profile graphic of your dive.
The GEO is pretty easy to use without the software, like any multi-function digital watch.
Someone posted a chart recently that compared computers, and Oceanic computers are pretty close to Navy tables or PADI RDP when you just look for the bottom time allowable for a single level dive (60 feet for 57 minutes, for example) - they were not as conservative as some other popular computers on the chart. You can probably find that post if you do some searching here.
