KVM Suggestion?

I need to get a large rack mountable, 16 port or larger, cascadable, VGA KVM that works with Macs. I've tried the iogear GCS1716, which claims mac support, but refuses to display video from my xserves or minis. Support says it's because of the mini displayport to VGA adapters. I've tried Apple official ones and third party. Since no modern Macs come with VGA built-in, it seems iogear's attitude is "Sure, Apple devices are supported. Unless you do the thing required to actually use them. Then, they are not supported.". Natch.

I have another KVM from another brand that escapes me at the moment that works fine, but it not cascadable, so we have out grown it.

Any suggestions would be appreciated.