Did I get it all?
AMD processors will have superior mulitasking performance not multithreaded performance. For pure performance, Intel still wins out in almost every price range. Games will be designed around 8 cores, but for computers, that means 8 threads. An i7 will not be inadequate to run these games thanks to Hyper-threading; Hyper-threading allows the i7 processor to handle more threads than it would normally would. kitamesume was not wrong when he (?) summarized this as allowing the processor to utilize more of its power.
The only real advantage AMD processors will have over an Intel equivalent is multitasking performance due to their sheer core count. Intel still beats comparable AMD processors in most every multithreaded task. If you need better multitasking, get an AMD; if you need more raw performance, get Intel. Games in general likes Intel processors a lot more than they do AMD's processors, and unfortunately for AMD, this is particularly true for CPU-bound games.
AnandTech has released Part 2 of their 1440p CPU article. Tom's Hardware with StarCraft II which is another CPU-bound game, I believe.
[H]ardOCP has some results, but because of the low resolution used, the results are a bit more exaggerated than it would be in real life. AMD processors are not really worth unless you're into mulitasking: their single thread performance is a joke, and their multithreaded performance is not so great either.
If you're going to be doing a lot of multitasking as you indicated you will be, then I recommend AMD. Their core count allows them better multi
tasking performance in exchange for Intel's general performance. Its a choice between good multitasking and performance in other words.
As for the RAM bit, I have a hard time imagining games using more than 6GB of RAM at this point in time, and I believe even in a few years 32GB will be overkill for gamers. I'm pretty sure that RAM usage is tied to VRAM usage as in the less VRAM you have the more RAM is used. I'm not too sure about that though. Maybe people more knowledgeable on the subject can educate me.
I hope that helps. It's kind of hard to collect information about the CPU's effect on performance. It isn't a secret that most games benefit from a beefier graphics card instead of a beefier central processor, so major review sites tend to focus on the former to the exclusion of the latter.
edit: In the article I linked to earlier in the thread, it also showed that AMD had trouble competing with its Intel counterpart on most tasks. It could still probably multitask better, but the multithreaded performance crown still goes to Intel. AMD's strength is in, once again, their multiple cores which allow them to multitask much, much better than Intel, and well, AMD pricing is better. Since you're planning on using the computer with virtualization and other things, I suspect the Opteron would be the better deal.
Also, I'd like to point out that the Dual-Socket setup hurts performance for games rather than helped. So the main use of that would be to use on a server and not any desktop use.
Also, too, for PhysX, you're either getting a secondary (strong enough not to bottleneck your current) nVidia card or you're getting a pretty beefy nVidia card. The latter is so cost-effective. Really, though, PhysX is not really common enough on games to justify picking only nVidia cards let alone basing your PC around it. There are other physics engines in use today, and they will need a better processor to use them. Also, no to your question regarding PhysX; more cores will not help with it. The primary use (almost singular use) for PhysX is to offload the physics engine caculations onto the graphics card rather than the processor. The entire point of it is nVidia cards. Nothing else has the cuda cores required to make it worth it. Again, you'll be looking at better multithreaded performance for physics engines not using PhysX, and you'll be looking nVidia cards for games using PhysX. Simple.
