Might go get some new RAM. How much performance gain? (And which ones to buy)

My system is:

Athlon 64 3000+
MSI K8T NEO (I'm not sure what this supports since it just says "DDR 400..can I use the DDR 433?)
80GB Seagate
ATI Radeon 9600 Pro
512 DDR 266mhz (256x1 333mhz, but since other is 266 both run at 266)

I don't want to spend THAT much. I'm thinking only around $150 CDN at the most for 512 MB of RAM.

Theres this store which is really close, has decent selection and prices. Please tell me which memory is my best 'bang for the buck' and would work good for my system. And within my price range:

http://canadacomputers.com/memory.html
Thanks

ask them to special order the pqi turbo pc3200 2.2.2.5/ or the ocz platunim rev2 pc3200 2.2.2.5 they both use tccd chips which run well with the a64 setup..

Will those 'special orders' be crazy in price?

if you wanted to spend a bit more you could get these

KINGSTON HYPERX 512MB DUAL CHANNEL KIT

it has TCCD chips, which are good overclockers. they are $171CAD

Are those kingston's a lot better than say these?

http://www.ocztechnology.com/products/memory/OCZ+DDR+PC-3500+Dual+Channel