just put another gig of ram in my E6550 system, plus a 512MB DDR3 4830 512mb which I overclocked (can't remember how far lol, but a fair margin over standard due to it being a Sapphire card with a huge fan / heatsink)
so now I'm running E6550 3GB 667mhz RAM, Gigabyte mobo, 4830 512mb, in an Antec case, with a BenQ 21" LCD, pretty damn impressed with the performance increase from fairly marginal upgrades (previously only had a 512mb DDR2 8600GT and 2GB RAM)