Hi, the decware looks quite expensive for what you get. Theres 2 main areas that ultimately determine the final quality of a tube amp, the power supply, and the output transformer, both seem to be compromised in that kit. (no choke in power supply, looks like a simple CRC filter, and small OPTs)
I'd suggest googling the RH84 SE design, similar circuit 12AT7/EL84 with lots of very good reviews, and lots of info on diyaudio/other forums, and ordering your transformers from say electraprint, although same claim to have good success with cheap Edcor or mid priced Hammond opts (125ESE from memory). You should be able to build 3 stereo amps for more or less the same amount