Totem Forest, Zu Soul, or Superfly

Have never heard a Totem, but at 87 db sensitivity, it's not very efficient at all and is likely a poor match for a 15 watt amplifier, monoblocks or otherwise.

I think the Soul (I have the Superfly) is quite special and would sing with 15 watts.

B-stock Superflys are available from ZU for $1400, this was a day or two ago. Quite the deal, only a limited number of pairs available if you are interested.

I have the Forests in a medium sized room driven by PASS X-250, They chew up all of the 40 Class A watts pretty easily in that room. I would imagine they are a tough load for your tube amp unless you are generally a low level nearfield listener. I have been considering the Zu's for a new/future family room setup, but there's a lot of conflicting love/hate stuff if you search through forums. They seem to resell well, so if you bought used and decided you were in the hate camp, then you may not risk much. From all accounts they will be very different from the Totems, not lacking in volume but maybe in bass, you might end up getting a bigger amp instead....?

I'm not really clear on how much difference there would be between the Souls and Omen. I ordered the Omens.Looks like the same main driver and tweeter.
60-day money back if you're not satisfied and they pay return shipping, but that may be only on the Omen.