What is the best stereo and speaker upgrade for an R/T.
A question like that is like asking someone "what kind of girl should I marry?" Ask the wrong person, and you're liable to end up with a very unsatisfying choice.
First, what features do you want? Receiver only, CD/DVD/WMA/MP3, CD/DVD Video, Game Console, Mobile PC, Satellite radio, the list goes on and on....
I'd suggest starting by paying a visit to several car stereo retailers like Car Toys or Earmark and looking around. When you see something interesting, ask a lot of questions. Take notes and be prepared to question the answers you're given.
Go to the Crutchfield website and do some digging (and request a catalogue, their catalogue has a wealth of information that is quite usefull). Then do some research on the web and read some reviews. You'll soon have the answers you're seeking.
When it comes time to buy I use National Audio Center on eBay. Great shipping, and great customer service. I ordered a head unit and tv tuner from and I mistakenly ordered a tuner that wasn't compatible with the headunit. They sent me the correct one even though it was $50 more than the one I had paid for. Customer service like that is rare.