If you do go down that route, aviod Kingston cards like the Plague! Very unreliable and nowhere near as fast as they claim to be.
Cant go wrong with..
http://www.scan.co.uk/Products/4GB-S...133x-Superfast
I've just upgraded from them to Extreme IV 16GBs and they are like rockets! Beware the 4GB & 8GB versions only quote 40MB/sec for some odd reason, 16GB quotes 45MB/sec (havent got near write speeds like that as the D300 won't let me, but read speeds are pretty close). Cost a bloody fortune though, that OCZ SSD and/or stripped out XP/Linux would probs be more cost effective.