That's a damn fine shot! Really good capturing the PCB pattern.

Well, for starters a head count of the wires shows nothing out of the ordinary. I can deduce as follows:

The shielded grey wire with the red/white inner wires is the sound output to the capacitors on the Micronas.

The shielded braid of this wire is covered in black heatshrink. Does that single red wire also attach to the same point? Hard to tell as I can see a partially obscured termination pin and cannot see if the red wire goes to the same point as the audio braid or the pin next to it.

I would say the blue/white striped wire next to this is your 5V supply. I say this as I can trace the PCB pattern in the photo and the trace goes around to the yellow indicator LED and also goes to several other places via links and such.

You are correct the wire you have called SIF would be indeed that by the looks of the parts configuration around where it terminates on the PCB.

The only other puzzling thing is that wire you have called -5V. I say this as there is no -5V line in a TiVo (in fact there is no negative lines at all - there's only 3.3V, 5V, 12V and 32V) and this is the only wire I cannot account for. Could you clarify what the big chip is? From this I can tell you what the wire is possibly for.