Responses from ricmech23

Kids, Dogs, and Speakers
Check out the Focal Aria 948’s. My son has a pair with three dogs running around. No issues and the base is very sturdy. Focal seems to build nice cabinets in their higher end models as well.   
Finally upgrading my amp
You could get used Peachtree Gan400 and the PreDac (preamp) used for around 2k and be done.   
(dons Helmet, kevlar vest and cup.) Biwiring Cornwall IVs any benefit?
I have two SVS self powered subs that I connect via RCA to the preouts on my preamplifier. I wouldn’t get caught up in pinpointing a specific frequency but you could use 50-60 as a starting point. The main point for me was making sure the subs ble... 
(dons Helmet, kevlar vest and cup.) Biwiring Cornwall IVs any benefit?
Run with two separate subs and you’ll never look back. I have the III’s with two subs still happy 5 years later. No bi-wire and No plans for upgrades. Sound stage is amazing at all volume levels.   
Magico A3 replacement
16,500 for Cornwalls?   
So many YouTube clips to evaluate sound quality. Why???
+1 @hilde45   
the big one: how do you choose speakers? By what features, data?
Don’t forget about customer service and the availability of parts if needed.   
Help me upgrade my beginner system!
Get some speakers. I’ve had the Nova 300 and it works great. And do the subwoofers in stereo.   
What speakers work with low wattage class A amps
Klipsch Heritage Series   
Best Class D GaNFET Amp Comparison. Who to invite?
Peachtree Gan400   
More Bass
You could try to add an equalizer, shiit loki seems like a great choice plus I think you get 15 days to return it.   
I feel bad for Generation X and The Millennial's
And you walked uphill in the snow to and from school lol with flip flops   
Speakers with deep/powerful bass
Cerwin Vegas!   
need amp recommendations for more separation of instruments
Don’t forget to factor in the recording itself. Try to find a reference album or song that you know the recording itself is top notch then you’ll have something to reference as you make changes/adjustments to your system. Good luck!   
New Cartridge or New Preamp
Check the Manley if you like tubes. I’m still running the same tubes in mine since new almost 5 years ago. Biggest thing I noticed is the background gets really dark and the clarity.