Hyperthreading hurts games and makes the cpu run hotter.
The memory controller on the 750 and 860 are on chip so latency is better than i920 x58.
The memory bandwidth of 21 vs 25 gigs/sec is not worth bickering. Games are not needing 10/gsec so the extra is overkill in terms of gaming, its more of a mental what if or bragging rights having trichannel mem.
They are all good chips and all will perform so closely that you won't be able to tell in game.
for gaming P55 should get the job done, there's pretty much no games that use hyperthreading. actually, most games still only use 1 to 2 cores, not even four. so a core i5 750 or a core i7 860 should get the job done.
however, if you want crossfire/SLI, i definitely recommend i7 because the motherboards have dual 16x opposed to Core i5 motherboards that have 8x/8x