I think that using a strap between the handles on each side of the SRX818SP would give you a center balance for a single person lift.
Yes, the 818 has ergonomic issues. I solved it by placing some really good, heavy duty rubber feet on one side of each cabinet. That puts the handles on top, and gives me a nice 3/4" space to easily slide my hand-truck in. I can dead lift the cabinet into my van, but it's still hard. Too bad you can't consider the 828.
I still use and love my PRX618xlf sub's. I agree with everything Scott Bolt said, they're light weight, sound great and are ergonomically fantastic.
The DXS 18 sub is interesting sounding, very deep. I use one in a club (house system), but it's hard to comment on total output without having one for myself. It is a monster though in weight and bulk.
KW181 really have a nice punch, and they're small and easy to work with. I think they sound great under any speaker, but you have to make sure you have the proper processing from sub to top.
I can't speak to the RCF boxes, but I've heard nothing but good about those and the JTR stuff.