This is what I would build for an HTPC personally
PCPartPicker part list: http://pcpartpicker.com/p/94ckyc
Price breakdown by merchant: http://pcpartpicker.com/p/94ckyc/by_merchant/
CPU: Intel Core i3-4160 3.6GHz Dual-Core Processor ($114.98 @ OutletPC)
Motherboard: ASRock H97M Anniversary Micro ATX LGA1150 Motherboard ($68.98 @ OutletPC)
Memory: Team Xtreem Dark Series 8GB (2 x 4GB) DDR3-1600 Memory ($54.99 @ Newegg)
Storage: Sandisk Ultra Plus 128GB 2.5" Solid State Drive ($58.84 @ Amazon)
Case: Fractal Design Node 804 MicroATX Mid Tower Case ($79.99 @ NCIX US)
Power Supply: Antec EarthWatts Green 380W 80+ Bronze Certified ATX Power Supply ($31.98 @ Newegg)
Operating System: Microsoft Windows 8.1 (OEM) (64-bit) ($87.75 @ OutletPC)
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-03-01 17:17 EST-0500
i3 can handle H.264 4K without dropping frames. You also won't need an aftermarket cooler as the stock cooler can handle that i3 while remaining very quiet.
You also didn't mention a sound card. Are you planning on pushing any kind of serious surround sound setup?