should I switch to a socket AM2 crossfire board?

[Caldezar]

So I had a second PC for sale not long ago that a coworker was going to buy. As it turned out, his wife decided she didn't want him to buy it. Fortunately, however, my g/f has decided she wants to do a bit of gaming, so I guess that's where it's going for now.

Done with the history, now to the question:

The board in said PC is a Gigabyte GA-M57SLI-S4. Being that this is now the weakest point in the hardware, I'm wondering how much of a performance difference I'd see if I upgraded the MB. The rest of the PC is as follows: (sorry for links, copy/pasted to save time)
CPU - AMD Athlon X2 6000+
VID - ASUS EAH4850 512MB
RAM - 4x 1GB Kingston 667MHz RAM (popped in extra RAM since it's staying with the GF)
PSU - OCZ Stealth-X-Stream 500W
HDD - 2x Seagate Barracuda 7200RPM SATAII

I'm trying to answer two questions really; Should I bother upgrading the MB? If so, what's a decently priced MB to go with that supports socket AM2 with crossfire support rather than SLI since I've switched all my video cards in the house to the 48xx series.

 

[BALISTX]

How much do you want to spend on a motherboard?

 

[Caldezar]

I'm pretty flexible for the most part, but keep in mind the rest of the machine isn't a hard core gaming set-up. So I'd say trying to keep it around the $200 or lower is reasonable. Of course, if there's a so-so board for $175, and an "OMG WTF WOW!" board for $250... I'll spend the extra cash for a nice jump in performance. So really, like I said, I'm flexible. Of course, I DO want the board to be an upgrade, not a latteral move.

 

[BALISTX]

You can get this board. Gigabyte MA790X-DS4 - $136.99 @ NCIX

This phone supports Crossfire.

 

[Caldezar]

How much of a difference would it make to jump from 570i to 790x chipset though? This is sorta my focal question regarding the choice to upgrade. I want to know roughly the performance jump before considering what board to buy.

*note* this machine will most likely never be overclocked. So OC performance holds no bearing on me when making a choice.

 

[BALISTX]

I would have to say it would be quite a bit of a jump from the 570i board. This board will support the Phenom processors if you decided to upgrade to those later on.