In theory, it shouldn't be THAT hard to roll together a 5-channel balanced class D amp using something like the Hypex UcD180 modules for $1000-1500. You basically just need:

an enclosure
odds and ends of connectors (power/neutrik balanced inputs, binding posts, etc)
Switching power supply
Transformer
5 hypex modules

Every time I think about sitting down and building a prototype, Mrs. Ritz comes up with another entry in her honey-do list. Sigh...

There are a few DIY kits out there, though. The attraction of having an amp that can put out gobs of power without the hernia-inducing weight or the wasted heat thrown into the room seems compelling. However, it doesn't appear to be that compelling to manufacturers who typically specialise in high quality on a low budget. The company that's able to produce an audiophile quality multichannel class D amp at an affordable price for the enthusiast market will probably do well.