Subwoofers - 1 Martin Logan Depth or 2 Grottos?

Hi, I didn't understand what you meant by "integrated amp does not have power inputs. So forget Vandy." Also, how big is your room?

Anyway, I have a Depth (one). I was going to get two, but one does the job quite well. It's right between my main speakers and (I guess) because of its omnidirectional radiation pattern, doesn't seem to excite room nodes. I have the phase angle set to 90 degrees as recommended by ML and it mates seamlessly with my CLS electrostats, crossing over at 35Hz. It has extremely fast transient response, and plenty of output for a 12x24x10 room.

My amplifier has pre-outs, but no inputs to the power amp so I cannot place the Vandy high-pass filter between the two to run to my main speakers.
Anyway, I cannot centrally locate the subwoofer except for behind the listening area. My listening area is sort of enclosed as 23'x17' with 11' cathedral ceiling, although it is very open on one side and partially open on the other, with a free-standing 8' wall at the 17' mark in front of the system and more space beyond that (behind the listening area).
My main concern is: Should I address reducing subwoofer cabinet vibration (eliminated by the more expensive Depth) or have two for stero imaging (if I get two less expensive Grottos). Depth has three 8" drivers; Grotto has one 10".

OK, I understand, but I don't think it should be a problem, at least for the way I think a subwoofer should be used.

I would just leave the Eggleston's hooked up as they are (no high pass) and (I assume the Vandy has line level inputs like the Depth) simply connect the preamp outs to the sub(s) line level inputs.

You don't have to put the (single) sub where I did if you can't, but I do feel that the Depth design is probably the least critical of location, the Vandy somewhat less, but it's still down-firing (semi-omnidirectional) and will do OK if it's on a hard surface. I don't think the Grottos are really any different or better than any other single driver mini-sub.