As rightly said by ico... if you put in two 7970s then you wont be able to put in anything else... no extra soundcard (you wont need it anyway), no TV Tuner (you can get a USB one though), no thunderbolt card (but thunderbolt devices are not mainstream yet), no RAID controller (MVG supports RAID 0,1,5,10 though).
Related to Overclock.. I'm running my 3570K at 4.8 GHz stable without any manual tweaking... just one or two clicks in BIOS, I could crank it up but then my Hyper 212 Evo wont be able to handle the temps. Dont worry about OC performance of MVG... it has been used to break world records.
May I ask.. why are you thinking about a sound card ?