As MrRipley said, an SSD won't give you more fps. Compare your daily schedule with the amount of things you'd start on your computer, be it booting the entire rig or just starting a program. If you think you'd lose valuable gaming time in those starts, go for an SSD. I'm an old fashioned person myself, so for me a couple of minutes at boot or 15 seconds during starting up a program don't mean a thing. In fact, after changing the start tune (title0) in AH I sometimes let it play through before logging in. A good five minutes, that is! Fact is that I may sit and stare at the screen without doing anything for quite a while, well, maybe thinking about what to type, how to form a sentence that would be easy to understand. Those moments take much more time daily than all of the boots and starts combined! Your productivity level may be at a much higher level than mine, thus I can't give you any one and only true advice, only some food for thought based on personal experience.
Typing this took way longer than booting my rig...
