Don't think that more cache always means better performance..
Benchmark Results - Tom's Hardware : Does Cache Size Really Boost Performance?
It's not for no reason people pick up e2160/e2180's and overclock them to 3.0-3.2 ghz for budget gaming. It does affect performance, but not as much as you'd think for gaming. Up to you on what you want to do...But do keep in mind that 8600M's are VERY OLD mobile chips, the 8800M is the current generation, with upcoming 9x00m's in development...The difference in performance between a 8800M and a 8600M are MASSIVE...and I mean massive. the 8600M is incapable of playing some games, meanwhile the 8800M will allow you to play pretty much any game, even crysis if you want to do some really nice settings. The 8600M is not a good gaming gpu, you'll be running crysis on low with a couple med options...With a 8800M, you'll be able to run on medium/high/very high...(VERY FEW very high, crysis kills rigs)
Obviously you are planning to run Bootcamp in order to play Aion, AoC..etc...But if you can go pc based if all the software you use is also on the PC, I'd suggest doing so, you get a lot more for your money...
Edit--
Just wanted to throw in a quick benchmarks.
AnandTech: NVIDIA GeForce 8800M: Fast DX10 Mobile GPUs Finally Arrive
Keep in mind the 8700GT runs the same architecture gpu under the 8600M...Just clocked much higher, 150 mhz on the core, 300 on the shader clock, and 200 mhz on the memory...It gets obliterated as you can see....Not even SLI'ed 8700's can come close...
I'll say right now, if you want to play AoC or Crysis, not going to happen on a 8600 without using the lowest settings.