I have a somewhat different point of view from some of the others you are getting. I would, like most others, recommend you look at a wrist mounted computer. It is easier to see and you don't have your computer tied to a regulator, handy if you want to travel but not take all of your gear.
I would avoid air integration. It is an expensive feature, a potential failure point, and loads even more info into the computer raising the potential for mis-reading critical data. The low-tech SPG is very reliable and unambiguous.
You will probably want to download your data into a computer. Factor this into the cost of the unit. Many manufacturers use proprietary cables that are unconscionably expensive "options," i.e. a hidden source of huge profit margin. An alternative is a non-downloadable computer and a Sensus Pro (
www.reefnet.com) which is a downloadable "black box" that for less than the cost of some cables gives you software and time series depth and temperature data.
Lastly, I wouldn't worry too much about multiple gases. I may be reading too much into your description, but you sound like you are a good distance away from doing this type of diving. If you do move toward that, you will be looking at lots of different gear anyway. And, if you get a good Nitrox computer now with a gauge mode, you can actually use a PC to do stage decompression tables and cover a bunch of that type of diving.
I am using a Suunto Vyper (despite the ridiculous price of the Vyper interface cable) backed up with a Uwatec Bottom timer, to do light deco, nitrox and air diving, etc. in conjunction with a computer program called V-Planner to plan for higher oxygen content decompression gas. I find that this configuration has all the features and redundancy I need.
