I also got my brackets from ebay. They work as promised. Have you thought about going to a junkyard to see if you can find some SL A-pillars? The wiring up to the A-pillar isn't hard to install. When I installed my amp, I ran new speaker wire to the tweeters.Went ahead and bought the speaker brackets off ebay.
I was able to look under the rear license plate, and I could see some light shining through, I guess if i remove the rear bumper and the plastic cover along the trunk I should be able to find somewhere to route the back-up camera wires. That's my biggest concern.
Can't wait for all the parts to arrive. Christmas in September. =)
Also, have you thought of the Kicker Hideaway? I have that installed under my passenger seat. Perfect sound and everything looks stock. What I have done to my car is here: http://www.nissanversaforums.com/car-showroom/8377-red_alert-2011-versa-sl.html