Overlocked CPU and non-overclocked ram?

Hey guys,

I overclocked my oldish core 2 duo e6420 from 2.13 to 3.2 Ghz on my evga 750i motherboard, but to achieve this i had to separate the memory timing from the CPU in the bios (ie the ram is still clocked at 667mhz). The reason for not clocking the ram is that its low quality and wouldnt make it to that fsb. Im just wondering how heavily this might affect performance? Im thinking of upgrading to an e8500 to pass the 4ghz barrier, im wondering if its worth buying new ram 1066mhz ram that'll be ok to overclock or just staying with the 4ghz that i have. What do you guys think?