No idea. The 3800 is 4 generations ago (3xxx, 4xxx, 5xxx, 6xxx, 7xxx), that doesn't mean it's slower, but I would bet money the 6530 is faster.
The 6530 will also be more efficient and work with DX11.
However if your gaming, I would recommend something much better than that crap like maybe a HD7750. The HD7750 is still low end, and it doesn't require much power supply.
What cpu and psu do you have and what is your budget for a video card?