PC in basement rest (Monitor, Mouse Keyboard, USB etc...) in office/study room

I think this will work fine! I did a little research on how power switches work (I wasn't sure if it was a closed circuit for on, break for off; or short closed on, short closed off). It sounds like its the later, meaning the motherboard simply needs a quick "pulse" of shorting that connection, so if you wanted to not break any current case, and simply use a lightswitch to bridge the connection, you would simply need to flash the switch on for a moment to turn the computer on, and flash again to turn it off safely (OS's handle this by shutting down normally). However, in case of crash or lockup, you could turn the switch on for 3-5 seconds to do a hard power off.

I don't think you could have both sets of buttons function at the same time without doing some cutting on your current case wires, unless you could find or make a 'Y' type adapter for the power switch +/- leads on the motherboard. Although, depending on your motherboard layout, an old USB motherboard Header may work nicely, you could click this onto the motherboard, determine which cables are going to power (and reset) +/-, and 'Y' that somehow with your 2 switches. If you have a local radioshack or similar (hobby shop maybe?) they would probably offer something similar to the wires your case uses for power/reset, this would probably be the "cleanest" way to do it as a USB header may bend the surrounding pins depending on how wide it is. I'm sure something like this would only be a few dollars, if not cents. They may even have a single female to dual male 'Y' version of this (you would need 4 of course, for power +/- and reset +/-).

If you really wanted to go the light switch route, but were worried about accidentally switching it off, you could get a dual light switch, and run one switch into the other, then both would need to be on to complete the circuit, alternatively you could run a button through a switch (old arcade style button would be sweet here), so it would only work when you hold the button and flicked the switch. Anyway, the possibilities are endless! Airplane bomb drop switch with safety cover?

If your looking for a more professional look, I noticed that various companies online offer awesome pc power button replacements, real metal, nice LED backlight, etc.. You could mount this somewhere, perhaps even to the desk if you want a more traditional power button feel and don't like the idea of flicking a light switch on and off.

Some aftermarket switches (and fancy power/reset cables):
http://www.frozencpu.com/cat/l2/g44/c153/list/p1/DIYMod_Parts-Switches.html

Have fun with this! Let me know what you decide!

I thought of something else you could try instead of using speaker wire, a 4 wire (2 twisted pairs) standard phone cable should be easily found and able to handle the small voltage. It would look cleaner, probably be quite a bit cheaper, and chances are (if you are anything like me) have around 30 of them scattered in random drawers. Just make sure if you want to do power and reset, that you do indeed have a 4 cable phone line, as some only have 2 cables (single twisted pair) in them, you can typically tell by looking at the connection end and counting the copper 'pins'.

Another slightly more expensive alternative would be to use some CAT4/5 (standard networking cable), these have up to 4 twisted pairs (8 wires). I did find some at my house that only had 4, so watch out for these. Typically the connections are clear so you can easily see how many wires are available. But this would allow power, rest, hdd led, and power led all in one tiny cable that you may have laying around already.

Did you have plans on including additional USB cables to go up top? As it would not be fun to run down stairs to plug in a flash drive or whatnot... Depending on the draw of your keyboard/mouse (assuming they are USB) you could find a usb splitter/hub that would allow a fair amount of usb ports from a single usb cable running from the basement.

This probably goes without saying, but I would also recommend providing some type of strain relief on the cables, as your monitor connection probably wouldn't enjoy hanging 30' of line just from the connection.