I think Latitude sums it up perfectly.The only thing I would add is that, for a small difference in price you can go from an "AIR" computer to a "Nitrox" computer.
Even in a basic computer if you decide to dive using nitrox you will not have to upgrade you computer. I my opinion this also goes for your regulators should you purchase them. Personally I like the software that comes with the Uwatec/ScubaPro computers. Also many of the ScubaPo computer have an infrared wireless interface to download your dive info to your computer. This saves you from the $100.00 plus other vendors will charge you for the $5.00 serial cable interface for their computers.
Another thought, if you are buying all your own gear I would say spend the big money on your regs. You will likely have them long then any other piece of equipment, and I believe they will make the biggest difference in your diving pleasure. There’s nothing worse then feeling like yo are sucking air through a straw.
http://www.scubapro.com/en-US/USA/instruments/computers.aspx
http://www.leisurepro.com/Prod/CategoryID_1985/Context_954/Sort_Relevance/DescSort_0/Filter_brand%3dUwatec/Page_1/UTCA2GW.html