would i be better off a) buying a used 6920 b) attempting to build my own? c) buying off the shelf.(new.) also, the more i read about piston systems, the better they seem to be. am i just falling for the "ooh, ahh"? if so, is there a conversion kit to go to piston? i'm going to be working with rather limited funds (about a thousand) and would like to get as far as possible. i've been told the most popular lower priced are "questionable" as far as quality. i figure i'd rather ask a newb question of an expert, than flush a grand down the toilet.