What is it filled with, and what kind of data do you plan on having?
An SSD is a massive performance boost for day-to-day computing. Anything that's related to starting your system or starting applications will benefit. Load times for games will improve, but your FPS generally won't (that only gets better with CPU/GPU upgrades).
If you just need more space to store pictures, music, and movies, my recommendation would be to get a couple of WD Red drives (one for storage, one for backup). Bulk storage doesn't need much performance and the Red drives come with a proper warranty service.