I need a small but good graphics card

You have two problems:
First, you need a low profile card.
Second, you have only a 220 watt PSU.

A 6850 needs 9 - 10 amps just for itself.

Looks like the most power AMD low profile card is a 6670. Good news is that a 6670 only needs about 65 - 70 watts so your present power supply should be able to power it, but you will have very little power in reserve.
 

randomhomosapien

Honorable
Apr 17, 2012
17
0
10,510

Is the 6670 good for gaming?