i dont want a new monitor.......
im happy playing with a 17"
As you said, you have the money so spend it. Games will look soo much better and be way funner to play on a 22 or 24" monitor. Seriously. Then after that consider upgrading. Please please please don't waste the money. We don't care if you blast your dads FPS because at the end of the day his game looks better and is just as smooth.
Buy the new monitor then get the graphics upgrade later. Then overall it will cost just as much but you get the best of both worlds

Your monitr only refreshes at a rate equivalent to 100fps tops. So 900fps still = 100fps