Responses from edwyun

Lehmannaudio Black Cube SE II
Concur.  The DIP switch settings in the manual are hard to decipher. 
Elapsed Time Counter for Tracking Stylus Life
If you can find one, the last version of the Phoenix Roadrunner had an accumulated playing time counter based on the revolutions of the platter. 
Aleph 4, or else? (good general purpose class A amp)
You should be ok with most speakers. However, to get the most optimum use of the Aleph amps, I recommend ensuring that your speakers have a nominal impedance of not less than 4 ohms. I'm currently using the Aleph 2 and they sound wonderful. 
How much gain is needed in a Phono Preamp for a 0.2 to 0.3mv low output moving coil?
Ditto - VPI Dynavector 20x2L with 15dB SUT and 46dB on phono pre (61db todal) works really well with still enough headroom. 
Can anyone listen to side 1 of Tchaikovsky "1812 Overture"?
I'd check your cart setup if you haven't already.  Also, I believe VPI recommends setting VTF on the higher end of the scale for carts.  YMMV 
Can anyone listen to side 1 of Tchaikovsky "1812 Overture"?
No problems with the Telarc 1812 on my VPI Scout II and Dynavector 20x2L, even at high volumes (using  SW too).. 
805 maxtrix tweeter
Biamping with very different amps
Not crazy. But you will typically need a means of adjusting gain as between the separate amps to make them equal. Usually done at the active crossover stage. 
B&W 801 vintage speakers in small space
I would replace the caps in both the B&W and Threshold.  Will sound like new again. 
JL Audio F110 Fathom pops...
My f112 is still running strong since 2009 with no issues (knock on wood). 
JL Audio F110 Fathom pops...
Definitely call JLA.  Could be the beginnings of capacitor failure on the power supply board. 
To get the real benefit of bi-amping you need to add active crossovers and bypass the passive crossovers in your speakers.  Then you'll need some measurement tools to dial in the crossover frequency, slope, etc.  A lot of work but definitely worth... 
B+W 801D upgrade crossover
Why do you want to upgrade the crossover?  Is there something your are trying to fix? 
Bi Amping my B&W Matrix 800s
There may be 4 PCBs but the 800 is essentially a 3 way with multiple driver arrays.  The 802 is also a 3 way but with 2 LF drivers. 
Bi Amping my B&W Matrix 800s
I purchased my 802s new in 1992.  They were not overdriven.  Caps, even polys, dont hold their specs for 20+ years.  Best way to see is if you measure their ESR.  Also, if the 800 is anything like the 802, they used cheap Bennic lytic caps.