pair of 18s with 3k can be loud and sound decent but your best bet is 2 15s with that power..
few 18s with that power are benifical.. the 15s have the motor strength and don't need the extremely stiff spiders the 18s need..
id say the IA DR, dd 3500, dc level 4, ascedant audio havoc, fi bl..
as far as subs you have to decide if you want something that does nice tuned low and can be retuned for shows or something that pounds get decently low and still does nicely without retuning..
how much space you have??