SSD's have gotten very reasonably priced with plenty under 50¢/GiB for 128GiB and 265GiB capacities. Keep an eye on Newegg, they regularly have really good sales on high capacity drives, like my 512GiB OCZ Vertex 4 for $299.99. For a more budget friendly but still high performance option, there are the Seagate Barracuda XT (now called Seagate Hybrid Drive) which combine a high capacity traditional hard drive with multiple GiB of solid state cache, which the drive automatically moves the most frequently accessed files for much faster access (Windows files, games, programs, etc). At under $130 for the Seagate Hybrid Drive 2TB
it would be perfect for you.
ASUS Sabertooth 990FX/Gen3 R2, FX-8350 w/ Corsair H60, 8 GiB G.SKILL RipjawsX DDR3-2133, XFX HD 7970 Ghz, 512GB Vertex 4, 256GB Vector, 240GB Agility 3, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, HP ZR2440w, Win 7 Ultimate x64