I have a Trek 7300 which is the same as the 7.3. I really like the bike and put 2300 miles on and took off 80 pounds. I did make several changes to the bike to improve the ride and comfort. I changed the fork, shifters and put on a more road based cassette. If you have the real feel for a road bike, don't get a hybrid, as you will be ready to swap out of it pretty quickly. If your not sure, I would look on Craig's List and you can pick one up for half the cost to make sure versus spending $600 on something you grow out of in 3 months.
I'm not sure exactly you are in relation to Boston, but I did find these on Craig's List:
http://boston.craigslist.org/gbs/bik/315539312.html
http://boston.craigslist.org/gbs/bik/315106997.html (Might be a slight bit tall for your 5' 8"
http://boston.craigslist.org/sob/bik/314776961.html This one is right up you alley 19" frame, $120.00
Good luck.