I don't think your graphics card should make any difference. The only time I've ever had any issues was using onboard graphics and that was with the VSTi instrument screen active, not with other audio.
It's possible that your picking up noise from something not shielded well in your system. I had tried a fireware interface last year and had horrible noise coming over firewire. Returned the interface and went with a PCI card which has worked fine without any noise and low latency.
In general, a Core i7 system should have lower latency.
so far I have best luck with onboard audio, after downloading realtek drivers, switched onboard audio to realtek instead of "disabled" or "HD aduio" in BIOS: no crackles.
using Asio4All in cubase, and "Lime" output on the motherboard.
Don't know if this helps but the front panel that connects to my creative Titanium sound card has crackle and it's from the graphics card. The modern large graphics cards play hell with internal sound cables. It works fine when I connect audio cables to the back of the computer. My sound card has EMI shielding to protect it from the hell that comes from it's neighbour.
Luckily, I got firestudio project to perform much better, but still not good enough to make audio recordings
I downloaded and installed this codec pack: http://www.mediacodec.org/ and disabled onboard audio, now firestudio project works better. even PreSonus ASIO works now! there is no constant audio crackling, only every few seconds few clicks and pops..
basically this is the whole procedure I did to improve the audio from initial unusable audio to current somehow usable audio:
-installed latest motherboard drivers
-switched off most of the cpu settinsg and other stuff i have no idea about in BIOS
-disabled HD audio and enabled realtek audi in BIOS
-installed latest realtek driver
-installed presonus drivers
-disabled onboard audio in BIOS
-switched to presonus asio