I agree about the Feltz. I just received the recently released Mahler complete symphonies conducted by Feltz; it's very fresh and with just enough sinew.

One could debate back and forth ad nauseam about the best interpreted / performed Mahler x, but one thing for sure is that Feltz / orchestra(s) execute mindful performances, and the recording quality is very high--I hear instruments and intermingled, intricate melodies that are typically buried in the "top choice" recordings. Happy listening.