I've not built a Z-kit, but I have one that someone started that I bought off them for the parts, and I've built several guitar amps from scratch over the years - so take this how you will.
Hammond does small enclosures that many amp builders use.
http://www.hammondmfg.com/scpg.htmThis is a great amp for beginner, because it's done on a circuit board and it's like a paint by numbers in assembly. Just put the parts in their place, solder correctly, trim the excess leads, and enjoy. There have been dozens of people who have made this amp in this forum as well as others - take some time and search through the forums for photos and suggestions, as well as Google and see what others have done for ideas.
Looking at the Transformers and parts that came with my (2nd hand Z-kit) it looks like it will sound just as good and probably better than my early SV83A amp. I think you'll really enjoy it and it's a great way to get into the flea watt SET amps!