Bought my stereo through crutchfield, no problems what-so-ever. If you're familiar with installing stereo equipment it's easy, the only thing that's even remotely different from any other car is installing the voltage regulator to the signal telling the factory amp to turn on, and even that was simple.
I got new speakers (inexpensive speakers, but better than my blown stock speakers) and then a little later added a head unit. The head unit made a MUCH more significant different in sound quality than the speakers did.
And FWIW Crutchfield reports that no flip-down head units will work in our cars... this is only somewhat true. At least in my experience a flip-down head unit will fit and the face plate will flip down just far enough to get a CD in and out, it just doesn't fold down all the way. I got the Pioneer DEH-X9500BHS and love it. I rarely use CDs anyway so when I do the minor inconvenience of having limited access space is tolerable.
2005 Windveil Blue GT (MT)
93H Bama tune, JLT Series 3 CAI, FRPP CMDPs, Pype bomb super system, 3.73 gears, Steeda shift bushings, Saleen short shift block
Steeda ultralite springs, Tokiko D-specs, J&M Extreme joint UCA/LCAs, PHB, C/C plates, bumpsteer kit, Steeda Q1S wheels, 2011 GT brakes, 275/40R18 Sumi HTR Ziii tires