Kit Amps offer the best value way of getting your hands on an unaffordable or unobtainable amp. I have worked on many of these as repairs or builds and everytime I would choose kit over a big name brand. But that is just my opinion based on the fact that I like to get my sleeves rolled up.
Once built you then own a classic sounding amp with an expected lifetime of forever.
Building your own kit is well within the scope of someone that can follow instructions and has patience. If you need a hand with the dangerous stages such as initial power up or mains wiring then you should contact a reputable tech to help. I do this fairly regularly for people.
Caution: Once you have built a few amps it does become addictive.
You can get fantastic guidance and inspiration on amp building at robrobinette‘s fantastic site as well as many other sites out there.
Custom builds are not so cost effective as you have to gather all your own parts work out the build design. However this gives you even more choice etc and this can be a way to build the amp of your dreams. See the matchless example below that I helped build.
TAD (Tube Amp Doctor) Kits
This TAD remake of a classic Marshall is pretty much identical to the original and has a few upgrades that make it even better.
Things like ceramic valve sockets, noiseless (compared to marshall) transformers and the cloth wiring adds to the sense of luxury.
Ok you never see this stuff but it is kind of comforting knowing that it is there inside.
TAD also supply cabinets and they are great quality too.
Ceriatone
Ceriatone are a Malaysian supplier that offer fantastic kit although the shipping and import costs put a few people off. They use vintage style wound transformers and provide excellent supoport.
Vyse
Vyse amps used to be called Torres Amps make classic reissues of Fender amps primarily. I have serviced a few and the build quality is stunning.
Modulus
Modulus make a range of kits and parts. I am regular consumer of their parts but yet to see one of their kits. They do give excellent support so I have no doubt that they would be good and they do allow much customisation on the parts eg. CTS high quality pots or selection of tone caps.
Custom Build – Matchless
This custom build was completed by a client of mine and I just helped with a final checkover. Note the use of Hammond off the shelf transformers and wiring neatness.