Look for a GTX260 216 cores

My system actually is:
MOBO - MSI DKA790GX Platinum
CPU - Phenom II 710
Mem - 4 GB dual channel 800 Mhz
Graphics - Powercolor HD4830
PSU - Corsair 650 Watt

I think in the posibility of buy a graphics card GTX260 216 cores, of course, changing the Mobo to a ASUS M3N72D for a possible option to SLI in the future, I don´t think in HD4890 because in my country the diference is about $100 and the Mobo Asus is less expensive and I guess to sell my MSI in a good price is an available option.

Someone can tell me if my desision is correct.

And Thanks to all who answer.