To which graphics card should I upgrade?

[maddogsasha]

So, I have been thinking and the GTX 660 and HD 7850 caught my attention. I have an old system:
3GB RAM
8600GT
Intel Core 2 Duo @ 2.53GHZ
1440x900
EP31 DS3L mobo
450 PSU

I mostly want to play Guild Wars 2 and don't know if I should upgrade my processor or GPU first. What GPU/CPU is best for Guild Wars 2 for about a $250 dollar budget? Also is my PSU and mobo enough to handle an upgrade?

 

[lt_dan_zsu]

Best card you can get with that money is a 7870. You might have to get a new cpu also. That seems like there could be a bottleneck. For now I would get that and deal with the bottleneck and upgrade to a new cpu as soon as possible