The best experience will come from learning how to TWEAK game settings to achieve the best results. There are two main ways to do this:
1) Tweak to about 40FPS with VSYNC OFF (con: screen tearing)
2) Tweak to maintain 60FPS most of the time with VSYNC ON. (con: lower quality visuals with higher frame rate)
Some game settings are very demanding with minimal quality compared to others. For example, 4xAA might be better than 8xAA. I always start a new game when running FRAPS and tweak things until I get to my target.
just a bigger gpu and maybe a bigger psu as higher end cards require a little more power than your psu can deliver.. but remember the higher you go the less return you will get for your money...
like i said its perfectly fine for most games. crysis 3 first level being the exception as it murders every card currently available even the 780ti and titan when its maxed out. but for most games like skyrim, cod and so on you should have no problem running near max with your current setup. also dont forget the 650ti has a fair bit of overclocking room.
i would add that at 1080p on a 24inch or under screen you dont need more than x4 on the anti aliasing. you just wont see any difference at all other than a frame rate drop... to be honest theres no need for 8x on todays screens as the dot pitch of the screens is so small.