I just acquired the 2004 Russian Melodiya 20-bit digital remastering of this set (Symphonies 1, 3, 4, 5, 6, 7, & 9) and I think the sound is really pretty good. Except for the thin and watery French horn sound heard in spots, there is none of the obnoxiousness I tend to associate with Soviet recordings from the 60s and 70s. Interestingly, in the movements which include vocals (3-iv, 3-v, and 4-iv), Kondrashin has recorded two versions, one in German and one in Russian.
Kondrashin's No. 9 (1964) is very impressive and, as John has said elsewhere, preferable to the live 1968 Tokyo recording on Altus. I expect to listen to the others over the next week or so. One of the engineers credited is Pyotr Kondrashin, perhaps a brother or other relative of the conductor?
James