Ti4600 will be much much faster.
For comparison, IGP 6150 is latest and greatest from nvidia, and it performs about the same as nvidia FX 5600, or a little slower than Ti500 and ATi 8500/9100..
IGP 6100 compares to FX 5200, or a little worse than nvidia Ti200 and ATi 9000/9200.
ATi (RX200) integrated is usually dedicated x300, which compares to around ATi 8500/9100 and nvidia Ti500.
Even a Ti4200 is better than any of these choices.
3dm2k3 results testing integrated here:
nvidia 6150 = 1600
ATi RX200 = 2100
For overclocking, nothing great with 6100/6150's yet.
Had the gigabyte 6150 up to 280FSB, which is not bad for stock vcore Opteron skt 939.
ATi RX200 though does have board capable of overclocking Opteron 146's to 3000MHz (300x10 here in Jetway A210GDMS PRO, with full vcore, mem dividers/voltage and HTT adjustments).
Don't know how 754 compares to 939 overclocking, but I think high FSB will require more adjustments than current nvidia boards provide.