I would go with an i5 over an i7, mostly because you don't need hyper-threading for gaming and it would be cheaper. Unless you plan on doing multiple CPU intensive things at once.
You can get 8gb of DDR3 RAM for more or less the same price of 4gb, also.
For the i7, 4gb of RAM and a motherboard: probably around $450-475.
This is what I would go with, myself.
For a good i5, 8gb of RAM and the same motherboard: around $380-400.
Edit: I haven't really used Tigerdirect so I actually looked at newegg.com (also newegg.ca)
If you'd rather I look on there I can as well, but I imagine there won't be a price difference.
