should be pretty close in performance, the chart has 4670,not 4650, but anyways. 5570 is made in 40nm process vs 55nm on 4650, so it should run cooler and use less power... if the price is about same i'd get the 5570, if not, then just get the cheaper one, the 4650 isn't a power hungry part either...
The 5570 is indeed faster than the 4650. Only problem with that card is that it's currently priced at $85. For that price you may as well go with the faster 9600GT. The only reason to go with the 5570 is if power is a concern or you have a low profile case
Check out the Best Gaming Card Guide just published here on Tom's. It will answer many of your questions. Look especially at the intro and conclusion pages which will give you a good feel for how to pick a card.
If you have a firm budget and/or specific requirements use those to get into the right tier on the chart. Then go to you favorite retailer (don't forget that you can follow links from Tom's and Tom's will get a little something for providing you with great information for free) and start price shopping. You might spend you whole budget and get a better card or save money on a card that meets your requirements.
I'm guessing that right now you'll find better deals on the 4000 series cards since the 5000 is brand new. On the other hand if you plan to keep the card for several years and are a high-end gamer then consider the 5000 series.
Be sure to check the specs carefully especially for type of RAM. I'm in the forums right now trying to figure out the differences especially between DDR3 and DDR5.
Hi does the 5570 work on a 220W psu. And I'm guessing by this forum it looks like thr 5570 owns the 4650. Am I correct?