You may want to try the builder section of the site.  This is something that is often asked, and you may find answers to questions you haven't even thought if yet.  I can think of a few different lowers I would go with before the Bushie, but the $150 price seems fair enough.  For some reason Bushmaster lowers seem to cost more, even though there is nothing special about them, aside from the name.

Build it yourself forum