I decided to post this question here and see what you people think:

I currently have 384 MB of DDR memory (256+128). I'm considering taking out the 128 and putting a 512. So in the end, I'd have 768 MB of memory.

Will there be a noticable improvement in performance? Will it be worth the cost of the memory?

My current system specs (minus the ram and anything I forgot to include):
FIC AD11 Motherboard
900 Mhz Athlon
Inno3D 64MB GeForce2 Ti
40GB Western Digital Hard Drive
10GB Western Digital Hard Drive
Sound Blaster Live! Value
HP CD-RW Drive
Generic DVD-ROM Drive