XPadder looks pretty good.
Also I like the idea of rigging up the Reset and/or Power button. What would I rig them up to? Would I need to get a keyboard encoder just for those two buttons?
Huh?
I mean shouldn't it be obvious? Computers have power and reset buttons as well.

Also keep in mind that on any computer running win xp and up you can set the power button on a pc to shut down windows when clicked. This sends a "shutting down" message to all open applications, so if the fe of your choice is coded properly, it'll shut it down cleanly as well.
Your going to have to modify the power button though.... it's a toggle button on the NES and you need a regular pushbutton.... it should be as simple as clipping/removing whatever internal latch the button uses to hold it in the on position. You can wire the power light up to the mother board as well.
I mean you COULD go to all the trouble of wiring up the reset button to something else, but it's only one button and it's all the way over at the console. How often do you reset in-game anyway?