The extra cache will only result in about 5% better performance. Depending on your budget, you should either get the e4400 or e6420. The multiplier of the e4400 is 10x. The multiplier of the e6420 is 8x, not 9x as someone else said. You should hit 3ghz with the e4400 and ddr2 800. The e6420 will also hit 3ghz easily, and likely overclock up to 3.6gz. Overall it should go higher than the e4400, but not guaranteed. The e6320 has only a 7x multiplier, not 8x. So with ddr2 800, you can only hit 2.8ghz without having to overclock your ram or use faster ram. So, if you're looking for the least expensive choice to get only 3ghz, the e4400 is your bet choice. If you really want to go higher, get the e6420.