SCA is an anomaly, in terms of a quality product in kit form. You won't find anyone else making quality stuff in such an accessible package.
With websites like Mouser and Digi-key it's not terribly hard to order all the parts for a project (minus tubes and transformers) from one source.
I'll look at the schematics, and make a parts list, then work my way down the list. Mouser has a cool function to save a shopping cart as a particular project for future use. It takes me an hour or two to get all my ducks in a row, but it's worth it.
Assembly is gonna take a little bit more knowledge and "common sense" but it's basically the same thing.
http://www.gyraf.dk/ has some great projects, and there are people on prodigy that make chassis and pcbs for most of them, which will eliminate most of the hard work.