Anyone listen to Zu Audio's Definition Mk3?

Also:
How do (2) 12” down firing woofers compete with (8) 10 inch rear firing woofers? One of the many things I love about my 1.5s is the prodigious, window shattering bass, when summoned, raises the hairs on my neck. The bass, however, was never as taught and punchy as I would have liked. Jazz, however, was always wonderful. I accepted this as a characteristic of tubes. Do the IVs feel like they are moving as much air as the 1.5s?

I cannot compare the Def 4s to the Def 1.5s; but compared to the Def 2s, the Def 4s have bass that is both more taught and more visceral.

Charles, the 6Moons preview of the Druid V makes special mention of possible upgrading in SQ by substituting caps, from the stock Clarity Cap, thru the Intertechnik Audyn Copper to the Duelund Black. Consensus was that the Duelund is the way to go, although the Audyn well outperformed the stock cap. Really feeling this is the next place to go re upgrading.
Is the Duelund Black the same as your Duelund Cast Copper?

Spirit,
Here`s the pecking order.
1)CAST, Silver foil(uber expensive!)
2)CAST, copper foil(expensuve)
3)VSF Black, Silver or copper
4)VSF, Silver or copper
5)Alexander, entry level
Given the cost of your Zu DEF IV. and the level and cost of your system, I`d go with the CAST copper and be done with it. No 2nd guessing, CAST are made for high caliber systems,get the best.My Coincident speaker is very good but the CAST simply raises it to a higher performance level. You won`t regret this capacitor improvement.
Regards,

Charles, a pair of CAST Cu amount to about 10% the price off the spkrs, whereas CAST Ag appear to be special order everywhere, price TBA, my guess is maybe 2-3x the price.
You seem v. happy with the Cu, and I'm sure Sean of Zu will concur with you.
Unless he gives me a compelling reason to go down the Ag route, it seems that Cu will be it.