Jeff, anytime you have a limited budget, something has to give, but where you make that concession is a personal decision. In monitoring, the expensive aspects can be boiled down to two things, accuracy and extension. In your case, I would buy the most accurate small monitors I could afford and deal with the lack of low end by carefully listening on a variety of systems, learning your speakers and room, even the use of headphones. If you choose to spend your budget getting some 'ok' monitors so you can afford an 'ok' sub, you simply end up with a full-range system that won't grow with you.
My .02...