Actually I found a full set of four JBL 5.25" in the junkyard, $10 each. They sound great. Also found a set of Polk Audio 6x9 and 4x6 in a Cadillac, that I ended up putting in my Cadillac, and moved the GM stock 6x9 to the Jeep.
Basically look for Jeeps that have had custom sound (ie, aftermarket head unit installed/missing, different speaker grills, etc) and then pop the door panel back. You'll find some interesting stuff