DAS units are essentially the previous generation of Deltec turbo units. They are a licensee of Deltec and I believe they are made in Texas. Now I dunno what's true or not, but Deltec claims to have changed the turbo design from what the DAS units use. Regardless, that's my understanding and what I've seen.
Why do you buy a BK? Because you need to pack the most skimming possible in the smallest package possible. Bonuses: silence, electrical effeciency, great build quality and representation that cares. I have a 450g tank and unfortunately, no there is no associated "tank room" or whatnot. EVERYTHING fits under the tank (except the chiller and the autotopoff). If space is not a consideration, then most realistically a mongo CC air driven unit is probably the option that gives you the finest bubble column, the most contact time and uses the least electricity. I do mean GINORMOUS though. Becketts are a "brute force" approach that also works for setups where noise and space aren't considerations. They still IMO are relatively maintenance heavy (when I had one I was constantly cleaning the injectors and the skimmer neck), but they are an option.
As for other needlewheel options, I love Deltecs coupled with the selfcleaninghead--practically zero maintenance. H&S units by report are quite comparable but unless it's a really large skimmer I don't believe they offer self cleaning heads.. First hand experience, ERs and ASMs don't hold a candle and I can't cope with lousy CS. I don't like to give my money to companies that don't support their products.
Oh and BTW, first hand experience and killawatt measurements, a Red Dragon 12 outflows a Dart quite handily and uses about 40-50w less.