If you can, opt for the higherclocked PC3500 RAM, its the best (imho) quality for price. I picked up some HyperX PC3200 CL2 and couldn't put it past 400mhz, thats why my 2100+ is stuck at 2.4ghz
but this also could be because I was stupid and got HyperX with the NF7-s. I know this now LOL
Anyway if its only a few dollars more, I would think it would be better to know for a fact that you can bump it past 400mhz.
If you get a chance try and see if you can find one with a good stepping and close to the center of the wafer.
AKA:
AXDA2500DKV4D F453237280481
AQXEA0331TPAW
K now the 0481 at the end of the number is the number of the chip, lower = closer to the center so lower = better
AQXEA0331 is considered one of the best OCing bartons available. Now the problem with this is that it is going to be SUPER hard to find one of these, and well there not made anymore. All of the new bartons are locked so all you can change is the FSB, not the multiplyer. if you can find one of the older bartons it would save you a lot of headachs. Hope this helps.