Hi! I'm building a gaming computer and heard that SSD's were better than HDD's in every way (except price). But my question is, would I be able to use JUST an SSD? I'm gonna get the 256gb Samsung 840 Pro Series SSD, and probably a second one around March (my b-day). Will I have problems using 2? Also I know that HDD's work best when there's about 20-30% free space, is that the same for an SSD?