I can't really answer your questions, but I'd love to hear your results with the double row of NSBs. I've built three different speaker systems since I built my first NSB arrays (16 NSB, 8 PT2 tweeters per side) and I just keep coming back to the array concept - I love these stupid 4 inchers:) I'd sure appreciate it if you would post your thoughts on the double row when you get around to them. I still have two cases of the drivers waiting to do something with.

FWIW regarding your amp choice, I'm tri-amping with an Outlaw 7.1 amp and it's working great. I'll be moving up to a 4way XO this year to incorporate a bass array (~50hz to ~500hz) along with my existing subs. I think there's alot of advantages to being able to easily attenuate or boost each part of the line so I like having an amp for each section. Whether it's two stereo amps or a 4 channel probably won't matter as much as having good control over the levels.

An aside...I'm currently going in the opposite direction you are. I'm building two more arrays that will be shorter than my NSBs. I can never get more than 9 feet away from them so I thought I'd try the sitting-only approach and see how it works out. I'm using eight 5.75" Peerless 850234 drivers (surplus from Madisound at 13.00 each) per side in two different configs. One is a "Needles" style and the other is a normal approach with 8 Pt2 tweets per side.

I was going to use a Fountek ribbon for the MMMMTMMMM experiment but I changed my mind and ordered two 106db 1wt/1m Pyle Pro tweeters - that should put the tweeter at about the right sound level at 9 feet to more closely match the levels of the mids. The Peerless drivers are 26 times the cost of the NSBs - I'm gonna be pissed if they don't sound 26 times better.:)

Anyway, good luck with the new arrays and please let us know about the double row version. There's at least one person interested!