What would be a good mobo if I got an i5 750. And with a pcie x16 2.0 or 2.1 (mabe 2 of them for crossfire) at least 16 gigs of ram? For a pretty good pice because I'm only 14.
Just an off the cuff ballpark for the system you described, is about $1000. I personally am sitting out the on the i3/i5/i7 socket 1156 and 1366 45 nm CPUs. I am going to wait for the 32 nm Sandy Bridge. By that time SSD hard drives, SATA 3 6.0 Gb/s and USB 3.0 will mature and lower in price.
For the money and I think you should consider an AMD platform. I have a AMD 955 BE (black edition) C3 stepping @ 4.0 Ghz that spanks my Intel Q9550 system in CPU benchmarks. I have read good things about the AMD 870 chipset, and it is cost effective. It will give you USB 3.0 and 6.0Gb/s SATA. Look at the AMD Phenom II X6 1055T and 1090 T, very cost effective 6 core processors.
16 GB of RAM is a little overkill, IMHO. I have had very few processes that have used all 8 GBs that I have installed.
Do some research and put a "dream system" parts list together, and then start searching and reading reviews at retailers and hardware forums. This will allow you to make your own informed decision. I normally spend 2 to 3 weeks researching before I buy parts. youtube is a great resource for how to and review vids
This is just my opinion, mileage will vary.
I enjoy "shopping and researching" as much as building.