Brahms and Tchaikovsky

Libor
You make many points I also will make, don't get hung up on audiophile quality sound, all these sound good enough, seek the stellar performances.

TCHAIKOVSKY Piano 1 - must agree with Libor here, the Argerich/Phillips live recording conducted by Kondrashin is 1st choice for me, Argerich gives defining performance with tremendous energy and passion, explosive finale.

Also like the Wild/Chesky version conducted by Fistoulari. For budget price CD the Glemser/Naxos is preferred by me over many full priced versions and offers tremendous value.

BRAHMS Sym 3 & 4
I think the Kleiber/DG Originals version of Brahms 4th is really strong contender for best 4th available, the sound qulaity is definitley not audiophile, but performance has great stature and almost universally praised by everyone.

Newest Abbado/DG version of Brahms 3rd is "close" to the best available and features excellent sound quality, here you have your cake and get to eat it to.

Also of note Klemperer/EMI version of Brahms 1st must be heard (and owned) The Mackerras/Telarc complete set is not my favorite performance but one of the few good period instrument performances available

I have three Argerich Tchaikovsky PC 1 performances on CD:
-Kondrashin/Phillips
-Dutoit/DG
-Abbado/DG
Best sound will go to 1994 Abbado live performance with BPO, but whenever I compared the Kondrashin to the Abbado I always felt the Abbado was more relaxed vs the excitement generated by Kondrashin version. I was surprised when checking the timing on finale movements that Abbado was significantly faster at 6:18 vs 6:54 for Kondrashin, but the overall sense I get despite that is that Kondrashin is the more energetic version.

Also Abbado version has weak (but entertaining) coupling, with Kondrashin you get Rachmaninoff PC 3 and Dutoit version gives you Prokofiev PC 3, both are very substantial and well done couplings.

I also have the Pletnev/Virgin set which gives you Tchaikovsky PC 1,2,3 at very low price. Sound here is also very good, but I really don't listen much to PC 2,3.

As far as mono recordings, I don't own any. I'm sure there are Richter, Horowitz etc versions of PC 1 that surpass stereo versions......but I must have stereo.

Gileon
I did many years ago have the Horrowitz/RCA mono recording from 1943 conducted by Toscanini of Tchaikovsky PC 1, but I perhaps foolishly got rid of it since I thought the sound quality was too comprimised......kinda wish I still had it now for reference.