Referentzhunter,
I created a website dedicated to Charles Ives and his music. You can find it at http://www.musicweb-international.com/Ives/
To view my favorite Ives recordings, click the "Survey of Recordings" link on the left. One note: I haven't updated the site in nearly 15 years, so it doesn't include anything recent. However, the site includes a near-complete review of extant recordings up 'til then.
By that way, that Michael Tilson Thomas version of Ives' Fourth Symphony is a desert-island pick.