Actually, that system is only about twice as fast as mine.
(Athlon XP 2600+,
Radeon 9700 Pro,
512Mb PC2100 DDR RAM,
40Gb HDD)
OK, the Athlon64 system has got a lot more storage space, but in terms of actual game speed, it'll probably only hit twice my framerate. And my rig is adequate for HL2 (on current showing, anyway), so I'm happy.
I'm looking at a RAM upgrade in the near future. Going for PC3200, and a new mobo. My spec described above is asssuming that I'm using a mobo capable of 333Mhz FSB, and mine isn't, so technically it's only an Athlon XP 2000+... So actually, the competition rig will probably triple my current framerates.
And getting a four figure framerate at 1280x1024 res in Quake 3 is pretty impressive even for an Athlon64...