Hutzal, that's not a bad idea actually...the hole is pretty far recessed into the cabinet, but that might work. I've never tried soldering, but i can't imagine that would be too involved, putting two wires together wouldn't be very difficult.
If i went with the wall plate I may even not worry about mounting it on the wall as it has banana-type connectors on either end. Just buy a load of banana plugs to make sure none of the wires touch and call it good.
This is certainly an option. Installing a wall plate is VERY easy. You can easily buy a low voltage j-box and insert it into the drywall (using post drywall j-box) and your done. THe hardest part would be cutting out the square for the low voltage j-box.
Something like this is what I have used in the past for exactly this purpose (for a speaker wall plate)
