if your only upgrading because some1 said your gpu is out of date, there really isnt a reason to upgrade.
8800gt is still a strong card, and the only reason you should upgrade it is if it cant play a current game you want at a desired settings level.
Though if you still want to upgrade, possible items to look into are gtx 260 for nvidia, and ati 4870 or ati 4890. Those should be around $175-$200. Any lower card would not be worth the upgrade.
For PSU im not really familiar with anything other than corsair or antec. Theres this antec 550w for $65
Newegg.com - Antec BP550 Plus 550W Continuous Power ATX12V V2.2 Modular Active PFC Power Supply - Power Supplies
Some1 else may be able to recommend another that might be around $50.