I trust you realize that installing an Apple OS in a non-Apple product violates the EULA. For that reason I doubt anybody here will help you with that part of your problem. Your storage issues are more complex than you realize, I think. Bulk storage of data is best handled by a less expensive 5400 RPM drive like a WD green which are cheaper than the 7200RPM variety. Also, WD offers a 10000RPM drive called a Raptor and I believe they just came out with a 1TB version however it's pricey. Many people would solve your problems with an SSD boot drive and a HDD secondary (possibly external) for bulk storage. The SSD is as fast as you can get although I don't personally think speed is the primary attribute of any SSD but rather reliability. The only time you're aware of the extra speed is on booting and program launch and those events quickly become "normal" after a few days. I think you need to decide how many games you want to store at any given time and whether an SSD would fit that budget. If not then the Raptor is the second choice for one drive to fit your situation.
Agree, for gaming a good 7200 rpm 500gb or 1 TB drive will work fine. The SSD just loads things faster, if you have the money go for the SSD for your OS and programs and buy a smaller 320 to 500 gb 5200/7200 for data storage.