As much as I want to run 2 subs, due to size constraints and WAF (mostly WAF), I still think I need to stick to 1 sub.
Checking out Elemental Designs, I'm thinking the A3-300 may be my best bet.. It's only $550 which isn't too bad, and if it actually delivers what it's specified to, I think I'll be pretty happy.
For placement reasons, I'm trying to get a sub that is around 20" high (so it can go under an end table in the corner of the room). Even though the A3-300 is 20.5", I think I'll be able to make it work. All other subs that I've seen seem to be 21" or higher, and especially as you get into beefier subs...
I'm still going to keep looking at the moment, but the A3-300 is the top runner!