I've got windows 8.1 on my HTPC in the basement (read: pitch black home theater) and it works fantastic. I have the wireless dongle which may or not be official (bought off ebay). I am a console gamer that said screw it to the next generation consoles (for the time being hehe) and there's only been one game that's not really working with the controller (Dragon Age: Origins), but it needs lots of keybinds for spells and abilities anyways so you wouldn't want to use a controller. The only hiccup I've ever experienced is when I've pressed the "On" button for the controller at the exact time of booting up the game on Steam. That has caused a game crash. So just wait either until the game has loaded or turn it on before it loads up and you should be gtg. For what it's worth, I just purchased a backlit keyboard with multiple light intensities and colours, so I will finally be able to play Guild Wars 2 with the lights completely off. so if darkness is what's putting you off keyboards, that may be your answer.
A lot of people seem to hate on the new OS, but I like it. If you get an SSD the boot up time is ridiculously fast, and if you install "Classic Shell" which is a free program, you end up with essentially Windows 7 anyway, but with the benefit of a higher level Direct X (11.1/11.2) which may or may not give you better graphics/performance. Just my 0.02.
Oh, and the first time you experience a holiday sale on Steam, you will cry tears of joy. The deals are ridiculous - consoles just can't compete with those deals. So even if you spend more up front for the system, your games will be less expensive and they will look better than even the next gen consoles.
Plus, you will get the added benefit of nerd programmers that, bless their hearts, make great games look and run even better than intended. Graphics suck? No problem, get the texture mod. Cars handle like crap? Don't fret, download the tire and physics mod.
Do your build right, and you will be paying less in the long run anyway. I hope I've convinced you somewhat. This coming from a guy who has had, let's see, The Odyssey 2 (Magnavox), Atari 2600, NES, Super NES, Genesis, N64, PS1, PS2, PS3, XBOX, and XBOX 360.
Good luck and do the right thing, build a HTPC.