Hey guys, this is Ryan of Vapor Audio. My google notifier sent me a link to this thread, and I wanted to post a few thoughts.
First, about building stacked ply cabinets - it is MUCH more difficult and time consuming than any other method of making a box. I know what some of you are thinking, take the pieces off the CNC, stack 'em up, boom ... done. I wish
Fact is, they come off the machine with small inconsistencies. The parts move when on the table, the bit gets smaller as it cuts, and end result is hours and hours of sanding to get everything back to flat. But the results are worth the work! In addition to the stacked ply cabinet, the Arcus has a 1" thick solid phenolic baffle which is very expensive material - about $300 sq/ft for 1" thick - and takes a $250 bit to cut on the CNC. Again, worth it though. All the DIY'ers here should make efforts to use exotic materials whenever possible and judge for yourself.
About the CSS planar, we've worked with it too. We've used both the Planar 1 and the Planar 2, and while they are nice tweeters, they're not in the same league as the Beyma AMT. The tonality of the CSS just isn't as pure and accurate, and it's obvious when comparing them side by side. Again, it is a nice tweeter that does a lot of things right for a decent price.
We are making a few small changes to the Arcus design btw, slightly taller cabinet to give the crossover more space, changing the internal shape and bracing layout, small stuff. The drivers themselves work very well together and will remain because of their unique abilities, and impressive result. The TD10M is very easy to work with, but the TPL 150/H took a lot more time to get right ... 1/2db differences can make or break the final result. Oh, and BTW the Arcus has a rear mounted AMT ambience tweeter as well.