I've got a pair of ppi PC.18,ds with very little playtime they are d4 subs I ran a ppi bk1800 on them , about 900rms on each. I had them in 16cu3 ported tuned at 30 htz and they hammered pretty good. 300$ + shipping .
Also have 2 dc audio lvl4 18"s (not really budget) 8/10 cos (minor scuffs on cone) 10/10 mech. Very little play time I had them in the same 16cu3 box they are d2 I had a bk1800 on each of them so about 1800 rms on each very loud and clean output. 400$ for the pair + shipping.
The shipping is the problem you might be better off buying new and getting free shipping lol. The DC's are 29lbs each and the ppi's are like 24lbs.. So yeah shipping is gonna ****