I have Cubase, Samplitude, Cakewalk Sonar, and Protools LE, Cubase has the best workflow for me and Samplitude is what I use for final mastering and CD burning. PTLE is very limited compared to other DAWs in that price range. If you must use Protools, as said before, go with the $12K HD system. For the same bucks though, you can buy some really nice pres, mics, converters, a good PC, and a world class DAW with the other brands mentioned. Go the the different websites and download sample versions and play with them a little while to see which fits your way of doing things. One great thing about Cakewalk is that they don't require the dongle, a hassle for on the road work.
One additional thing to think about...if you are considering using Universal Audio Digital effects, don't use Samplitude. For some reason, they don't seem to be compatible with UAD stuff.
As far as worrying about getting your work mastered at a PT equipped studio, they should be able to work with wav files or some of the other formats offered by most DAWs.