You shouldn't lose any hashes. BTC mining requires negibible bandwidth. We are talking KB per second.
Messing w/ HT link can cause system instabilities though. You likely will find more power savings turning off junk you don't need.
On my MSI 890FXA-GD70 I have
USB 3.0 - disabled
Secondary LAN - disabled
EIDE controller -disabled
SATA controller - disabled
SATA RAID - disabled
on board sound - disabled
serial port - disabled
monitor LED ( wtf
) - disabled
I have Sempron single core underclocked to 1.6Ghz and undervolted (? can't remember to what). It likely could go lower but I just tried 1.6GHz and dropped voltage 2 steps and it worked fine. Never pushed it beyond that.
Oh and the always helpful Power after AC Loss: Always On