Hey Suppy.
Not long ago had the parcel shelf of my SV6 in bits, fitting my amp and 7x10s.
I didn't see any wiring up there that specifically looked like it was for speakers, ie - positioning and such. What is there though (beneath the black trim panel) is a harness leading off to a multi-pin connector, which I assume might be an extra piece of hardware for the so-called "premium" sound system. (12Voltking might be able to clear this up - you havin' a squiz at this thread King?)
To be honest though, if you're fitting the 6x9s anyway, you'll need to remove the back seat and trim - once you have those out it's very little extra hassle to run some decent wiring for the speakers. Were you just going to run the 6x9s out of the head unit or were you planning on amplifying? (I would certainly recommend the latter, and you might like to also have a look at this thread -
http://forums.justcommodores.com.au/showthread.php?t=14974 ) Oh, plus you'll need to get the grilles that fit into the parcel shelf trim, if you haven't got 'em already. (don't get those from Holden, just have a poke around on eBay - I got mine for less than half of what the General was going to charge me - only thing is they were greay rather than black, but a squirt of satin black enamel soon fixed that.)
If you want some hints to get the back seat out, just stick your hand up. :thumbsup:
Cheerz!