Compare this for me plz

The 4650 will outperform the 3450. One is a low profile card (4650) the other is standard (3450) if you need a low profile card, get the 4650. If you don't need a low profile card get a standard size 4650.

so the 4650 will it play like crysis or empire total war or any of the newer games and how will it do on counter strike source because my 6200 only gets a small 12.6 fps

It's not a high performance gaming card.

Here's a Graphic card hierarchy chart that shows the relative performance of different cards.
http://www.tomshardware.com/reviews/best-graphics-card,...

You can check the entire article for pricing recommendations. However your 250w power supply will not supply the needs of ANY gaming card, so you'd also have to replace your power supply to play the games you listed.