What I would do is get a 250gb SSD, and then OWC's Data Doubler and put a 1TB 5400RPM in the optical bay.
I did this upgrade for my boss in his 2012 MBP. It screams now, and he has more space while still keeping battery life good and heat in check. he keeps the stuff he doesnt need really fast access on the 1TB drive, and the rest on the SSD. -- F**K THE NHL. Go Blue Jays 2013!!!
I did it with my 2011 mini (256GB Kingston Hyper X and a 1TB HDD) and it works great. Following the steps it was really easy. I CCC'd my stuff to a temp USB external and then created the fused volume and then CCC'd everything back. After a couple of reboots and running a few apps, OS X moved everything around. The moving is done after the machine is idle for awhile. ML has the OS and frequently used apps including my Fusion XP VM on the SSD.