Hello Vadim,

I have been using a MidiMan Midisport 4x4 for more than three years, it is not rack mountable but they make a 8x8 model which is rack mountable. I like midisport because they always update their drivers.

Here is a link to 8x8:
http://www.music123.com/Midiman-USB-Midisport-8X8s-i85140.music

I have also heard good things about the Edirol UM-880. I might upgrade to it in the near future since I am running out of Midi Ports on 4x4 already. Here is the link to Edirol UM-880:
http://www.music123.com/Edirol-UM880-i41462.music

Let me know what interface you end up buying since I am looking for a rack mountable interface also.