Thanks again for the detailed reply! I must say, I'm certainly not a newbie when it comes to the Model F - I've had five XTs, and done a fair bit of disassembling. The only thing I don't understand is the electrical stuff, or how to get them feeling optimal once they've been opened. I've messed up a few, because they feel terrible after opening them or replacing the foam mat. :/
But if the 5155 Model F cable can be unclipped from the controller like the PC equivalent, I'll switch around the cables and call it a day! I think I'll nab that clean one off Ebay, as soon as I can afford it. If not, I'll work on an external converter and refer to this thread! Cheers for the advice, guys.
I am only tempted to get the 5155 keyboard because it looks nicer than the XT and will sound better (due to the plastic chassis).