I would go with a i5 quad core CPU. I say this since my I7-2600k witrh 4 true cores with HyperThreading so I have 8 threads running at 4300-4800mhz with 2 GTX770 GPU's in SLI. Even with that nice overclock SVP with everything maxed can bring a overclocked 2600k to its knees. I am running it with MPHC and madvr "the full SVP install pack" and I have my madVR setting up high with jinc 4 taps etc and the video card can handle it. Its the extra frames at full HD that sometime will bring it to its knees. like motions vectors grid if I keep that at default its fine go to 7px small 1 CPU use passes 85%or 6 px small1 thats when cpu usage maxes out for the most part above 90%.
I think a true quad core would be best. I am still figuring it out but I also have 2 i3 2120 3.3ghz dual cores with HT one running a low profile hd 6570 gpu and the other has a HD 7750 GPU they both do a fine job also. I just cannot max anything out like i can on mu bigger machine.
If you plan on adding a GPu to your haswell dual core with HT the AMD HD7750 does a fine job even with madVR maxed out almost as much as it can be. I feel the AMD/ATI GPUs do a better job for HTPC/lioght gaming then Nvidia. And I happen to own 2 EVGA GTX 770 Classified cards in SLI in my gaming rig that cost me 450$ each.
If you did not get your CPU yet Intel is releasing a haswell refresh with some interesting new chips liike a overclockable 20th anniversary pentium dual core. they are replacing the 4770k with a 4790k. On top of that I think they are removing the horrible paste between the Integrated heat sink and the CPU chip and soldering them on like sandy bridge and ivy bridge -E. this was the main reason for higher temperatures compared to the soldered on IHS on sandy bridge 2600k etc. when they release ivy bridge quad cores and haswell quad cores they started using gray paste instead of fluxless solder.