Hi,
I don't have a lot of experience in T-Shirt printing, but we have a few customers who do. Have you tried dye-sublimation? I think you can get a decent printer for pretty cheap. I think the cost per print is lower for large runs of silk screening though. My understanding is that you can dye-sublimate for less on small runs. I could be wrong though.

http://www.t-shirtforums.com/dye-sublimation/