I'd add a 2TB data storage hard drive, for photos/movies/whatever. You don't want to ever fill up the SSD to capacity because the way they work, they need some unused spare area to help optimize performance. So have another HD in there for big files.
I would NOT go smaller on the SSD, if that configuration meets your price point. I'm holding out for the 1TB SSDs to drop in price because I've had plenty of hassles with a too-small SSD in my laptop. Yes I "can" make it work with a small boot SSD and a larger data drive, but it is a HASSLE. As soon as I am able, the small SSD in my laptop will be replaced with a bigger one so I can quit fiddling with it and just USE it.
Also, nvidia will be announcing their next gen vid chipset in a month or to, if I recall correctly. That's probably a good reason to not over-buy the video card, however the top of the line 780 nvidia cards are pretty dang fast...
Oh yea, don't forget a new monitor if your new card is overkill for your current monitor. I like how 24" monitors fit on my desk... for some games, too big of a monitor means you have to keep turning your head to see details on all edges of the monitor. With a nice hires 24" monitor you should be able to keep the whole fight in front of you, yet still have enough desktop space to get a nice big image. Or for multi-monitor setups, 3 24" monitors stood up in portrait mode can give you a pretty big window into the world
Vertical screen size is important for flightsims IMHO... you can have 3 monitors in normal landscape mode for driving games...