Get some quality ram for that.
Read up a little bit about RAM so you understand something about it. There are good articles here on AT under
"Memory"
and under
"Guides" (see what they recommend to build computers.
I'd suggest you buy some USED PC3200 based on TCCD or TCC5 chips (likes lower voltage, runs cooler). You could seek something like OCZ Platinum Rev 2, which you might find USED in the price range of $100 per GB. Geil One Ultra would be another good choice, similarly priced.
Reason for USED is there's a transition happening as the market moves toward the newer DDR2 type of RAM, so what you'll be buying is older technology. Still really good though.
If you buy a pair of 512MB ram sticks, you want to buy ones that were originally sold as a matched pair. If you buy 4 sticks, then 2 matched pairs.
UPDATE: Here you go...check out this thread in the
AT Hot Deals forum.