I think G5 apple machines are way more interesting and easy to find than custom ultra-expensive motherboards.

If it's a PA-Semi product with Altivec it may be interesting but I seriously doubt it. They'll probably prepare 603-like cores with 128KB of L2 cache and no Altivec. And the price will probably be too high for 95% of amiga users.

I'm happy with my Apple hardware and it's easier to replace if it gets broken.