Buchholz, Lowrie, and Ellsbury were all taken in 2005 (along with Bowden) and only recently have gotten their shots in the majors. 2006 we drafted Masterson and Daniel Bard in the first two rounds. One of those guys is already serving as a set up man in the majors, and the other is being touted as a future closer. Hagadone is in the pipeline right now, he could be a future lefty starter for the big club. You forgot they took David Murphy in 2003, who had 74 RBIs and 15 homers in 2/3 of the season last year (and an .806 OPS).
Pretty much all these guys I listed, as well the ones you listed, the Sox took with their first pick.
Now that we've established that with the first pick is where Theo does his damage, do you really want to throw it away for Derek Lowe or Ben Sheets?
350 is a bogus sample size for the discussion. Its the first round pick that we lose if we do this your way. Its those first round picks (or first picks overall) that have been so impressive. Forget about the late rounders.