Yeah, use the 6570 if you plan to use madVR.
Didn't see you mention your budget but I think I would look at some of the lower end Ivy Bridge chips (G1610, G2020, G2120) and a B75 or H77 motherboard.
All of the three chips are dual core models with no Hyper Threading, first one has 2MB L3 cache and 2.6Ghz, the rest are 3MB L3 cache and 2.9Ghz and 3.1Ghz.
Not really any huge difference between those three regarding the performance and what not.
Yesterday I actually played around with my 3770K and downclocked it from 4.3Ghz.
I set it to 2.6Ghz first and then 3.1Ghz, played some different material on MPC-HC+madVR. Didn't notice a thing even with staring at the ctrl+J info.. Actually when I looked at CPU-Z while playing I noticed that when 2.6Ghz it stayed mainly 2.5-2.6Ghz (speedstep) and when 3.1Ghz it jumped hell of a lot between 2.4-3.1Ghz. So.. CPU usage isn't anything worth mentioning. Probably 10ish % in each 4 threads the player was using. So perhaps if I were to disable HT and two of the cores I would see ~40ish percent load.
Although I didn't bother turning off the other two cores nor disabling the Hyper Threading so take this with a grain of salt. Probably won't notice a thing between the G1610 and G2120 so might as well go with the G1610
I'm getting the G2120 along with B75M-ITX and a stick of 4GB DDR3/1600 for my own HTPC upgrade
Coming from GA-MA78GM-S2H, Athlon II x2 240 and 4GB DDR2/800