Mesch,
I have rebuilt 3 of the Dyna 70s and more than a dozen of the MK IIIs.
they are decent amps, and can sound good, but don't go crazy with after makret parts, or you will soon have way more cash in the amp than it is worth. or alternatively you can begin to ask what tube amp can you now buy on the used market for 1.5K dollars....quite a few.
would suggest looking at dynakitparts.com and tubes4hifi.com for starters.
as one of the other posters noted, the Cayin amps are really well built and can be bought used for a very reasonable price.
I'd say have fun with your rebuild but dont go crazy with aftermarket parts, NOS tubes and the like.
happy soldering.