^ What jason said. Over by my house there's a guy I LOVE who owns a shop called "sound advice" and his prices are always better on parts, and he doesn't charge alot for labor. I've never had him install anything becuase I can do it myself, but his prices are way cheeper than any of the big companies. And the best part is that he gives advice for FREE! I love it, my first stereo job (custom fosgate sys in an old 70's BMW) would have never been completed if it hadn't of been for his advice.
I've never recieved help like that at any corperate store and I know too many people who do or used to install sereo systems at places like that. They all don't know a thing about stereos, or working on a car for that matter.
You know what I think would answer you question pjo? Go drive a 79'-83' 280ZX. They're not too much bigger than the older Z cars and they come with all the luxury options. Power mirrors, power windows, cuise control, power steering (or at least it seems like power steering), power brakes (i think the older Zs have power brakes too). The only thing they don't have is power seats & keyless entry. Very advanced for it's time.
Power on those is around the same as the earlier Z cars (guess from a 280Z i've driven that was stock). They seems to have a little more pickup, wich might be due to the factory 5 speed on all cars. They do feel thier weight though, they get real sloppy around turns. This is probly fixible and even with all the features you'll be adding you won't quite reach the weight of the 280ZX cars. But it would show you the extreme for you.