All depending on how much you are willing to throw down.
Specs on one of my gaming rigs;
Asus P8P67 PRO
i7-2600k <- unlocked, if you aren't looking to oc you could look into the i7-2600. Save a couple pennies. Same goes for any i5.
8GB AMD PE memory, at PC3-10600 and 8-8-8 timing (4x2GB)
GTX 560 Ti from EVGA 2GB
850W PSU from Corsair
Running an H100 for the CPU.
I will only recommend Western Digital for an HDD. They build quality products. (Don't flame, only my opinion)
Other odds and ends that are not prevalent.
Not sure if you are going to transplant your new hardware into your old case, be sure to there is going to be adequate airflow. Also make sure if you go this route you have the correct form factor.
Just what is stated above will set you back a little past 10 big ones retail. This is not including the OS, optical drives and any other bs you would want to throw on it. This computer though will run any game thrown at it on the highest settings, but this is most definitely not a high end machine.
IMO, if I were you...I would shy away from the enthusiast level boards. You probably wont be needing or using any of the features that are enthusiast level specific, especially since you are not looking to overclock.
Whew, let me go ahead and get down off my soap box...It is pretty high up here :P hehe