Those Zilla cabs you mentioned are incredible! I bought one of their Fatboy 2x12 cabs and it is easily the best sounding cab I have ever played through.

I also used to own one of the orange micro terror heads you mentioned and through a proper cab they are very usable.

I currently have a 5w valve head I use in the house and for any bluesy stuff I play and a 50w valve head I use for when I play with my band so your idea of having one really nice cab and a few heads to chose from will definitely give you plenty of tonal options, the only other thing I would consider is a speaker soak or attenuator so you are able to find the sweet spot on the amp head and then bring the volume down using the attenuator/speaker soak.