though the usual reviews don't quite cover the multiboxing needs. with 4+instances you're going to fully utilize the 6 real cores.

for roughly the price of an amd 1090t (3.2ghz) you get an intel i7-870 or i7-930(2.8ghz) which both only have 4cores + hyperthreading, which is as far as i can remember not of any benefit in games. additionally iirc the amd isn't as far away from the intel cpus in games as in other software.

additionally the motherboards are usually a bit cheaper for amd, too

both platforms are most likely dead upgrade wise after the current cpu. but if you're having loads of ddr2 already i'd get an am2+ board which has a bios update for the amd 6cores available and continue to use it there