It's always helpful to have more of your volume control's range be useful and accessible than less, if all other things are equal. But would you be happy with a preamp you like less just to get more useful range from your preamp's volume control? Unless the useful rotational range is very small, probably the answer is no. You have two feasible choices if you like your power amp:
1/ Get a lower-gain preamp if you can find one you like as much;
2/ or more feasibly, get a pair of Rothwell RCA inline attenuators (review: http://www.enjoythemusic.com/magazine/equipment/0803/rothwell.htm) These can be placed in-line between your preamp and power amp, to scrub off 10db of gain before the audio signal hits the power amp inputs. If you look around, you can also find similar attenuators at 12db and 15db reduction. Simple, effective, cheap and you get more useable twist in your volume control. Don't obsess about having another resistor in your signal chain.
You could also get a TVC from Music First (expensive) or DIYhifisupply.com (affordable), for attenuation without gain.
I do hear the Berning as tonally leaner (a little too lean) than the Audion Black Shadow 845 SET. Audion electronics are uniquely fast among tube gear but fully fleshed tonally, so I don't agree that the Berning has more apparent speed than the Audion. The Berning sounds "faster" than the majority of SET amps outside of Audion particularly, and some Sophia. I have to extrapolate that Melody qualifies too. Others might. Audion's 2a3 and 300B amps are also impressive like the two top line amps that have silver content, for their quickness, so it's not just a top-line exlusive for them.
You can tune the Audion 845 SET nicely to preferences for warmth and tone or objectivity, via the 845 tube selection. The 845A, B, C, T, KR Audio, and NOS RCA/United/GE tubes lend the amp different voicings. With the Berning, your locked.
As for the Def4 cab structure vs. Def2: I haven't yet seen a drawing of the interior of 4, to see the actual strucure improvements beyond the obvious, but the obvious things are very significant. First, the speaker no longer has 4 ten inch holes cut out of its rear panel, where Def2 had 4 sub drivers. That by itself strengthens the tower box. Internal damping has been upgraded and I believe there is more corner and junction bracing. But the other obvious change is the speaker tower's foundation. The stronger box no longer compromised by cut-outs in the back panel is now firmly bolted to a 1-1/2" thick machined aluminum plinth that is vented for sound to escape and serves as mounting for the 12" downfiring sub. It's a robust, very stiff physical foundation for the more rigid box to rest upon.
I surmise the front panel is now marginally stiffer in addition to being damped by the considerable mass mounted to it. The baffle should be a little stronger in the upper half of the cabinet because the size of the Radian supertweeter forces the FRDs to be mounted further apart than on prior Definitions, reducing how much structural mass is lost in a concentrated area on Def 1 & 2 where the FRDs slightly overlap the supertweeter cut. But the big progress on reducing cabinet talk was between Def 1.5 >> Def2, with the upgrade to 15 ply voidless birch from MDF. That difference for intrusive cabinet resonances was dramatic.
Phil
