So your primary goal here is gaming, yes? Do you have a budget cap?
While I'd never recommend someone get a completely stripped down mboard, I often recommend they don't blow the bank on them either. You can get a great board under $200 without suffering any practical performance deficits. Most of the more expensive boards bolt on additional features, but even the most expensive boards often won't let you use them all simultaneously.
If your main concern is gaming, I'd recommend you save your money and not worry about CPU overclocking. The difference between a stock i5 and OC'd i5 is typically very small. I don't think it's worth the additional $100+ you usually have to spend to get good OCing parts. That's just my opinion of course, and if you want to OC your CPU, more power to you.
In terms of gaming GPUs, I usually recommend against SLI and CFX as well. Yes, it can give a lot of extra graphical processing power, but like CPU OCing, it comes with a lot of extra considerations. You need a mboard that can support it, you need a PSU that can power them, and you need a case that can fit them and provide adequate cooling for the additional heat. Even then, not every game supports them. It's not uncommon for games to not support multi-GPUs at launch. It's not uncommon for games to have glitches and problems with it either. If you're willing to spend extra money on twin GPUs, I think it's almost always a better idea to spend that money on a single, stronger GPU.
Again, like CPU OCing for gaming, this is only my opinion. If you're dead set on SLI/CFX, make sure you do it right. Make sure you get proper supporting components to be able to run them. Get the two cards at the outset. Don't buy one now and think you'll upgrade later. Many people never get around to the upgrade later. Even if they do, you're dropping money on what will likely be older tech for the time.
In short, I usually go by two defining principles. 1, Keep It Simple, Stupid. 2, Just because I have the money available, doesn't mean I need to spend it.