The only thing that depriciates faster than computer hardware is your lunch. That being said, I think your system is quite good. Out of date is very subjective, depending on what kind of user you are. If you must have bleeding edge, than yes, your system is out of date. Bleeding edge systems go out of date very fast. Your system should be able to run games comfortably for about a year, but that's just an estimate. It depends on what your play.
For myself, I play mainly flight sims, and the odd shooter. I would build a system around my favorite flight sim, but not a shooter. I play a shooter once and it's done. Not so for flight sims. Flight sims come out infrequently, so I will not upgrade until the next Oleg Maddox sim comes out in 2007. I have the same mobo and processor as you and 1 7800gtx. I considered dual core but it offers no advantage in the games I play. Only 1 sim (Falcon 4) is coded for dual core and the performance difference is very small. My old rig P4 2.8 1G pc3200 9800 pro plays all flight sims adequately but the performance of my current rig is so much better. Get 2G RAM if the games you play benefit from it. Anyway, a computer is outdated if it no longer meets your needs. No one else can determine what your needs are.