Machina
Upon further consideration of some recommendations, I've decided to switch up some of the upgrade options for my computer. Now that there is an announcement of TF2's release as a HL2 mod, I am definitely going to go for this upgrade(plus these repeated lockups on my current system are driving me crazy). The motherboard may seem like it's a bit overkill, but I figure I do these upgrades about once every four years, so I may as well get something that's quality and has the possibility of more future expandability. So, the configuration I've chosen is as follows:
ASUS M2N32-SLI Deluxe Wireless Edition Socket AM2 NVIDIA nForce 590 SLI
G.SKILL 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)
AMD Athlon 64 X2 4600+ Windsor 2000MHz HT Socket AM2 Dual Core Processor
ASUS EN7900GT-TOP/2DHT/256M Geforce 256MB GDDR3 PCI Express x16 Video Card
If you see any flaws in these choices, please post a comment.