I have a couple Tubes4HiFi pieces in my system now, and parts for a ST35 amp soon to be built. Their kits are a very good value in stock form and really lend themselves to upgrades in parts quality and esthetics. When I built my PH16 phono stage, I upgraded the signal path caps, power supply caps, NOS tubes, rca plugs, iec inlet, installed a SUT on board, and upgraded all the wiring over their standard kit. The sound quality is tremendous. Last piece of the upgrade will be a choke filter in the power supply and top mounting the power transformer away from the sensitive components. Point being, the circuit design and the core idea of their items are very well thought out. Go all out on some parts upgrades in the right spots (caps, hook up wire and rca plugs) and you'll be a very happy camper and have a fun project on your hands.
-Lloyd