Ippolitov-Ivanov if you are not familiar with his smaller works, you are missing out. For example
Sonata for Violin and Piano in A Major, Op.8
Spanish Serenade for Viola and Piano (1897)
String Quartet in a minor, Op.13
Piano Quartet in E flat Major, Op.9
An Evening in Georgia, Quintet for Flute, Oboe, Clarinet, Bassoon & Piano, Op.71
There are recordings of all but the string quartet and piano quartet. Soundbites of the string quartet can be heard on the Edition Silvertrust website
http://www.editionsilvertrust.com/ippolitov-Ivanov-string-qt.htm And a movement of the piano quartet is on Youtube.
As for Gliere, in my opinion, without any doubt, his best music is his chamber music
His four string quartets and three string sextets for which he won several prizes. While the sextets were composed when he was a yount man, the quartets were composed throughout his life and it is interesting to see how he evolved under the Soviet Stalinist regime. The first two were written in Tsarist Russian, the last two in Soviet times.