The question is not wattage, but how many amps can be delivered at 12v. This is a function of the efficiency of the PSU and how many watts go to the 12v side vs. the rest. Nvidia recommends 26A on the 12v rails for a 8800gts. Check out this psu reference list for a list of quality units:
http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=viewtopic&p=1491365#1491365 Look for a psu that has at least 26amps, and that does not have an asterisk in front which indicates that it is not suitable for a Quad core cpu. About the lowest priced unit I see on the list is an Antec NeoHe 430w for $70. You can get this psu included in an Antec P150 case for $139 delivered. Otherwise, I would look at a Seasonic unit, if for no other reason that they make several of the psu's sold under other brand names.
On the Hard drive, consider getting a single 150gb raptor. It will cost you $170 vs. $270 for the two 74gb units. The performance will actually be better. Go to www.storagereview.com for a thorough tutorial on raid-0 and some benchmarks that are representative of what a single user in a desktop environment might expect. Synthetic benchmarks like hdtach are accurate enough, but are misleading as a predictor of value to you. On other benchmarks, look at the values where the queue level is 1, or 2 at most.
---good luck---