Well.....do you play alot of games? My Steam library is currently ~415GB and ever-growing. Obviously a 256GB SSD isn't going to cut it.
I personally think spending loads of cash for a large SSD just to store games is a waste. Hard drive speed typically doesn't matter much for games, because everything is loaded into RAM. The only difference you're going to see is in level load times, which is fairly trivial and doesn't affect the gaming experience (assuming you've got a halfway decent mechanical drive).
i5 2500k - P67 - GTX660 - 840 Pro 256GB - Xonar Essence STX - Senn HD595's