Don't think I need a disk drive, I'm sure I'll almost never use it and I can steal from my rig to install.
Any suggestions about controls? I'll be sitting about 10 feet from the tv and htpc. Will wireless mouse and keyboard work okay, or is it too far? I like the idea of using a universal type remote to power on/off the system, but I can't seem to find any simple solutions to that.
Your budget range of $400 - $500 is similar to mine, except that I went with a more compact mini-itx motherboard and case. Otherwise, my recently finished HTPC build is similar to what you describe. I ordered all the parts from Newegg, Amazon and Buy.com. It consists of:
Case w/ PSU & 80mm Fan: I wanted something that would fit neatly into a bookshelf, so I chose a low cost mini-itx Rosewill RC-CIX-01 black steel case ($49 from Newegg) - much better quality than I had expected - everything fits in easily using the stock Intel cooler. This is a really low power motherboard that runs cool and fairly quiet. The 150W P.S. is adequate since I don't need a separate graphics card.
TV card: You didn't mention watching TV but I am strongly against paying for cable! There is a single PCI-E slot on this motherboard so I installed an AverTV Duet PCI-E tuner card for Over The Air TV watching. For streaming video, Netflix, Hulu, Kylo and Boxee run smoother than on a previous Zotac/Ion build for my son-in-law.