I just put in an American Autowire Hwy 22 kit -- with a trunk mount extension kit.... it's pretty nice kit and the wires and instruction (for what they're worth - when you're doing everything custom...).
But when I was at SEMA I checked out the Ron Francis booth - and my next cars will run their stuff. I felt the wire quality was better....
In order to keep the clutter down under the dash - I built a rack that tilts down - and this area is behind an upholstered headboard...
I made it tilt forward so if the battery needed to come out - you can just drag the battery over it... thus the components are all to the driver side.
The key is that all the wiring is labeled every few inches... and it's all color coded.
After that - it's up to the "installer" to a nice neat job with good crimps and protection from chafing and making runs that don't end up looking like your mothers spaghetti.