only decent decks you gonna get for four grand are the second hand ones of someone who REALLY likes you. The ONLY 2nd hand decks you shouldeven consider buying are SL-1200s, i dont know anybody who's getting rid of the new Vestax's, so Technics are the only ones worth spending money on.
Go to places like Mabu and Hi-five and check any notices or fliers or ask the folks behind the counter, or go to DJ Syndicate and ask there.
Good Luck son, decks do NOT come cheap.