I have to disagree re the drive potential of the Aleph 2 vs the 3. The 2 monos EASILY pump 200w into 4 ohms (a typical impedence seen in many speakers in the upper bass), and will play MUCH louder than the Aleph 3 in the lower octaves.
I also recommend investigation of the preamp match. Alephs' low input impedence can be problemmatic. I chased a used Aleph P to ensure full driveability.
I'm grateful for the comment re cables, as I too am using a lean transparent cable (Nordost Red Dawn), yet I find the overall system balance slightly lean at ALL SPLs. There's no change with loudness (outside Fletcher-Munson effects).
C'mon, Sean...200w/ch into 92dB/w yields what...115dB??!!
This is truly dangerous, no? I'll defer to your experience, but phew...can you hear me?
On third thought I wonder if the Aleph 3 is truly saturating, given the 92 db/w sens of your speakers. Does the impedence drop to 2-3 ohms in the bass? Is your pre not fully driving the amp?
I too will chase a warmer, yet detailed interconnect to flatten the upper mid bump a bit. (Note that I attribute this mild tonal anomoly to the use of a 5" midrange in my system. 6.5 or 7" midranges generally are a little flatter
between 400 and 1200 Hz, in my experience, though they may have more problems crossing to the tweeter than a 4-5" mid.)
So I'd look at the preamp first, the IC second, and if you're still running out of steam on peaks, chase some used Aleph 2s like I did. Good Luck. Ernie