All depends on what resolution you plan on playing at, i.ve got the version below your's the 780g hd3200 and i personally can play and have played call of duty world at war, fallout 3, far cry 2, world in conflict etc fine
Fair enough i have mine overclocked to 650mhz graphics core and the 128mb ddr3 sideport memory up to something like 1333mhz speeds, i did have it overclocked higher to 700 on the graphics but dropped it due to it being summer here and not having better cooling on it yet (only a crap heatsink not a good heatpipe based one like on most 790gx boards) and running it passively for now, with a fan i know i could push it up much higher to at least 750/800, and 700 is the stock clock for the hd3300 series if i remember correctly and it can be clocked up to like 1ghz or so if you cool it well or are lucky from the reviews ive seen anyway
Im playing at either 800x600 or 1024x768 depending on the game and settings eg even with my lower clock i can play far cry 2 on medium with the very rare stutter during heavy scenes with lots of explosions flames and gunfire but it doesn't bog down on me
But don't expect miricles or anything your going to be playing most modern games on low settings with 0 aa etc its the best igp out there right now but its not anywhere near a dedicated card, which is all part of the reason i'll be grabbing a 4670 soon when i move up to a 22 inch lcd (or 2 or a 24) in december because the integrated graphics would be a pain in the fps at those resolutions!
The only really slow stuttering ive seen in game even on low with no aa is cod world at war, and i'd put that down to the drivers because i can run modern warfare with medium settings and a playable framerate, im yet to update to catalyst 8.11 though since i had so much trouble getting vista 64 to run with 8.8 when i first got the board so i didn't want to tempt fate, im running 8.10 now so i'd say its just drivers and it being a new game and all
But all in all mate your better off pretty much with even the lowest 4000 series card than the igp if you can spare the cash because it has its own dedicated memory its not slowed by your ram it'll be faster etc not to mention the improvements of moving from the 3000 to 4000 series mate
I mean you can pick up a 4670 msi 512mb for 65 with rebate from newegg or a 1gb 4650 for 70 or even a sapphire 4550 512mb for 40 with rebate or a 512mb 4350 for 30 with rebate or if your really hard up a 256mb 4350 for 20 with rebate and all of them would outperform the onboard graphics mate (sorry for the lack of links but its impossible when posting from my phone)
Hopefully that helps you a little bit mate i myself was in 2 minds about getting a card or using the cash for other things but i found even a cheap card is a major step up!