RAM is really cheap, so it should be pretty easy to get a good amount and high quality for a good price. For gaming, I'd get around 8GB, 2 sticks at 4GB each, that would allow for dual-channel, just check your motherboard manual because depending on your number of sticks you have to put them in a certain position.
As far as with the i7 discussion, Sandy Bridge topped out at the i7-2600k, the Ivy Bridge topped out at the i7-3770k, and the new Haswell processors top out at the i7-4770k
Then there's the i7 Extreme line, with the Sandy Bridge-E that tops out at the i7-3970x and the Ivy Bridge-E which tops out at the i7-4960x
If you're looking at the high-end though, I would go for the i7-3930k or the i7-4930k, which are $500 cheaper than the next processor and there's hardly any speed difference.