I'd also like to know how the system works in a Viper, but I do have the 18 speaker system in my SRT8 Jeep. I think it sounds outstanding.
My opinion on car audio is unpopular, but here goes...
As a professional audio engineer I have the privilege of sitting in front of high-end studio monitors 8 hours a day. I'm in a very good room, with very accurate monitors.
In a car, things are very different- the "room" is terrible with bad refections, a small space, and the speakers are almost never placed properly, they are at your knees, or reflecting off the windshield. Then once the car is in motion, the engine noise, road noise, and vibrations ruin what was already a poor environment.
I believe that factory systems have an advantage over after market systems because they have hundreds of man hours of R&D from real engineers who understand the compromise that needs to be made in the system to compensate for the noise and bad acoustics. In the driveway with the engine off, an aftermarket system can sound great, but on the road, it's very difficult to make it sound good at a safe volume.
On the negative side, factory systems have to be made as cheaply as possible, while still lasting through the warranty period.
Another area where my opinion will differ with most, is that I prefer my stereo system to be accurate like my studio monitors. Most car audio enthusiasts like a system to have so much bass that it rattles every body panel. I prefer not to add additional bass to the mix. I want to hear what the engineer and producer determined is the ideal sound for the album.
All that to say, if the Viper is anywhere near as good as my Jeep, then it's well worth $3000.