Hello Agents?

A few months ago, I drafted up a concise and cogent query letter and sent it off to my "pre-vetted" list of literary agents, this at the recommendation of all the "Book Proposal Doctors." My list came from standing in Barnes & Noble on the Upper West Side and reading through the "Acknowlegements" sections of books I felt were similar (e.g. "complementary") enough to entice the agent for that book to represent mine. I sent over 25 letters, mostly by e-mail, though others by snail mail as their protocol required. Many wrote back to say thanks but no thanks,. Some did say they were interested, and I sent off my proposal (revision #66) to each of them. No bites though. I understand that rejection is part of the process, but I just wonder if it is a sign that I need to go ahead and write the book and get it out into the market, rather than follow the "process" that is expected of authors that expect to follow the traditional route. Glad to take on suggestions here about the importance (or not) of using an agent and a publishing house to get a book to market.