I do not want to sound rude, but why spend 500$ on water for a 4200+, even for a K8 they were expensive and slow... It is very easy now to get a really cheap Opteron 165/170/175 with a PRIME stepping that will do 3.1+ on water.

60$ 2gb 6400 ballistix
266$ Q6600
135$ DFI965

That should be your next upgrade