I've actually had experience with TTP, Cartek, and Vette Doctors, so I'll just give you a quick run down of how I feel about each...
TTP-Matt is a great guy. Always works with you on prices and is an excellent tuner. Puts down great numbers, but kind of odd that they don't publicly release their Equalizer cam specs. I bought my Moser 12 bolt and Kooks headers for my Trans Am from them. Always an easy transaction and the guys there are as helpful as can be.
Cartek-Dave runs the place and is one of the nicest guys in the industry. They also probably have the best name and reputation out of any of the shops we're talking about. They have been doing this forever and know their sh!t. Julio, their tuner, is among the best LS-series tuners in the country. They have a separate room and one guy (I forget his name) who builds all the motors. They really are classy guys and everyone there is an expert in what they do. One guy builds engines, Julio tunes, Dave walks around and helps everybody out (he's an expert in everything) and then there are two excellent mechanics who do all the installs and fabbing and so forth. I had them install some things for me and Julio tuned my Trans Am.
Vette Doctors-Carmen is an interesting guy. He seems real cold and curt at first, but you just need to warm up to him. The shop has a great reputation and Carmen is an excellent tuner. I didn't have a great experience with him, but I won't go into it because they really are a good shop. They're smaller and not as well known, but people in the Long Island area swear by them.