I just picked up a Honda 13 hp with Cat 6DX pump (same as cat 66dx; the 66dx only has a different housing) off of craigslist for $100. The pump needs a packing kit, but is otherwise in great shape.
I picked up a "4000 psi 4 gpm" unit up from myrtle beach with 50 ft hose decent gun and downstreamer for 225. Honda 13 hp with Comet ZWD pump.
Moral of the story: second hand can get you a better machine for the money than you're gonna get new for 1000 bucks.