I think you're more worried about airflow than you need to be. I have a card similar to what you're buying, a 7950, and I run my fans (just two) at 5V instead of 12V and I have no problems with heat.
More fans won't hurt anything obviously, but I would try it without. In terms of stuff you can buy later if you decide it's necessary fans are at the top of the list.
Since an SSD fits easily into your budget I would give it a really hard look before I would decide to cut it. Just to give you some idea of what the benefit is, think about how often your computer has to pause to load something from the hard drive. It's more frequent than you might first imagine.
- Load up the OS at startup
- Reading or writing incidental temp files
- Opening any application
- Working with documents/spreadsheets/etc.
- Loading game info/levels
- Blah...
So where you really see the benefit of the SSD is in the speed with which it can do those incidental fetches from the drive. The whole system just feels quicker because you don't have to wait a few seconds while Word opens for example. You just click on it and it's open. Literally, Word opens for me in the blink of an eye.
For some games that doesn't matter as much because there's also processing to be done at the beginning of the game, or an intro movie or whatever. But for others there's a marked difference - BF3 levels open much faster than they used to for me.
If that doesn't appeal to you it's 100% up to you. But just understand that that's where the SSD really shines.