Try the Realtek before we talk about PCIe cards. There's a chance that it'll work fine. You need to listen carefully to the quality, make sure it doesn't have distortion/clipping. Make sure all levels are 50%, no higher, in Windows sound. Unhide hidden items, mute anything not used.
In
VirtualDub, while capturing, watch the monitors. See if ms offset or anything varies too much.
Onboard is almost always bad -- except sometime Realtek. Sometimes. I used Realtek for a couple of years with an ATI AIW setup.
