Adding another ARC AMP to Tympani - D-400 or 2x 100.2 (SS) ..or 2x D-150 (tube) ??

With 6 + 4 panels, you may have the big daddy of the Tympani’s---the T-III. A rare beast, congratulations! If not, what are they---T-I’s or T-IV’s with extra bass panels? By the way, the mid-bass produced by Tympani’s (and bass down to almost 30Hz if the panels are braced) remains the most life-like I have ever heard, though Apogees---which I have never heard---are reported to also do bass very well. I gotta ask you: how are you running all those panels without bi-amping them?!

Are you currently satisfied with the D-250 in regard to midrange and highs? The solid state D-400 and paired D-100’s are better used on the bass panels, if you want to keep an all-ARC set-up. Why not, it’s a classic! The D-150 remains a particular favorite with ARC enthusiasts, as does the SP-10 (Brooks Berdan owned that combination until the end), but the D-250 is no slouch. So if you’re happy with the D-250, just add whichever bass-panel amp you prefer. Or, put the D-150 on the m/t panels, the D-250 on the bass. Those bass panels can eat as much power as you throw at them; Satie over on The Planar Speaker Asylum feeds his T-IV bass panels 2000 watts a side!

The T-ID has 3 panels per side, so how do you end up with 6 + 4?

The x/o between the midrange driver and the tweeter is almost always left as is, though some fanatics replace the stock parts with boutique ones of the same value. Separating the mid from the tweet electronically (and amplifying them separately) doesn't afford any improvement over stock.

When I said brace the bass panels, I didn't mean to each other (thought that IS a good idea), but rather to the ceiling or back wall. Another way to do that is with the Mye stands Grant makes for the Tympanis. Not cheap, but real good.