If you're building subs, you probably have the skills to build bass panels/traps. I know manufacturers claim their magic material X and what not but there is plenty of DIY data out there for plans 
Personally for me (and I have not listened to these multi-sub systems) I place far more emphasis on midrange tonality than perfect bass response. If you can have both, that's great. I prefer simpler stuff, but I also like tube amps and vinyl so what the hell do I know.
Agreed. Panels aren't hard to make. Audimute makes theirs out of cotton and recycled paper, and anyone with some woodworking skills and math skills can make their own diffusers as well. A 2D type skyline would take a lot of patience, but you could definitely do it. On a list of important factors for me, perfect bass is pretty much at the bottom. If the highs aren't right and if the soundstage isn't enveloping, I get bored, no matter how amazing the bass is. When I was at the Musikverein, I was not thinking "oh man, the bass in here is so flat and awesome!" I was thinking, "oh my god, the voices float out into the room and it's like I can reach out and touch them. I've never heard speakers do this."
