I'll disagree then. Your mobo is same generation as mine, the cpu could be updated to a phenomII and for a gpu I'd look at something like a 7870ish.
You can't bottleneck by buying a better GPU, you can waste money though if the cpu can't keep it happy.
The GPU will last a long time and personally I'd get the best you can afford and something your PSU can handle.
Incidentally just installed win8 pro (the $40 download) overtop/upgraded Vistax64. Went really well, no major issues.
#1: FX-6350, Antec Kuhler 920, MSI 970 Gaming, Powercolor R9 290X, ASUS Xonar D2X, GSkill (F3-14900cl9d-8gbxl), Antec Truepower New 750, Arc Midi, Win8.1pro x64
#2: MSI A88X-G45, AMD A10-7850K, Asus 5870v2, Antec900 case, AMD 2x4GB 2133 (R938G2130UK), Antec 750 True, 128GB Sandisk SSD, WD Black 1TB, Win8.1pro x64
#3: Athlon 64 X2 4200+, AGP 1950pro, Audigy 2, Asus A8V-D, 2gig ram, Enermax 465P. Now on Win8.1pro cat 10.2