Having tried the DLS 5000R myself and having heard the EP350, the EP350 is the better sub, you made a wise/good choice and I beleive the 350 in room response to be very close to 18-20hz depends on the room of course.

great choice, let us know what you think

My EP350 arrived yesterday. The setup went without incident. I hooked it up and played a number of my CDs that stress the bottom end. My initial impressions compared to the Velodyne DLS 5000R are:

1. Visually it fits into the living room a lot better as it's smaller and the finish matches my M60s.
2. It's been much easier to blend sound with the M60s. I never did get a good blend out of the DLS 5000R/M60 combination and was able to identify where the bass notes were coming from.
3. It's a much more musical speaker, meaning it reproduces the actual notes of the music rather than giving out muddy low rumblings.

I'll continue tweaking it this weekend, but so far I'm very pleased with my purchase.

Excellent, glad to hear you are enjoying the new sub.

#2 is interesting. I found the same thing with my EP350: no effort to blend.

#3, well duh!! Axiom takes music reproduction very seriously.

At some point I would like to compare a sub that reaches down into the teens with my EP350 to satisfy my curiosity, but for pipe organ music, I am quite satisfied with the EP350.

I've wondered how a pair of EP400s would sound for pipe organ music. The specs say they go down to 18 Hz and a pair of them should fill my 2500 cu/ft living room quite nicely. I realize a couple of EP800s would be more impressive, but I sort of like to have somewhere to sit in the living room as well.

Unless you plan on sitting on top of the sub that won't matter because they take up almost the same amount of floor space. The EP800 is only wider by a 4.5 inches.

The EP400 is a small, sealed enclosure with an 8 inch driver. DSP can only do so much. It is meant for WAF above all else. The EP400 is a small sub which means it needs to be placed in a small room. 2500cu/ft is not what I would consider small and would be pushing to the limits of the EP400. It might play down to 18hz but don't expect much output at that frequency. The EP400 will be outclassed by bigger subs (its just the laws of physics) at the over $1000 dollar price point including the EP500/EP800.

^^^^
+1