My HTPC has the following specs.
Antec Fusion Pro Case Intel Core i3 2100 Sandy Bridge Processor 128GB SSD (Primary HDD) 2TB x 2 RAID1 (Video Archives) Logitech Harmony Remote (Controls HTPC/Receiver/TV) ASUS P8Z68-V LX MotherBoard 4x2GB DDR3-1600RAM Ceton InfiniTV4 PCIE (4 Tuners with MCard - Able to watch Premium Channels) Windows 7 Ultimate XBMC Plugin for WMC Ceton Plugin for WMC Wireless 2.4GHz Mouse
It's not the best and fastest computer in the world, but I have 10 second boots and able to use the remote for everything. It's easy to use (wife is not tech savvy). Redundancy on the video archives and switching applications and boots are a dream with the SSD.
Before my dog ate the wireless dongle, I did have an ASUS Media Center Keyboard that had a trackball built in which was extremely nice. Had the feel of an iPad when holding but a full physical keyboard. Came stock with my HTPC predecessor ASUS CS5110. When I met my wife, it was determined that I needed to move to just one remote and we keep the wireless mouse handy if something funky happens with the remote communication.
We are using integrated graphics via HDMI, but works great for streaming/tv/video playback.