The original WAD 300b is supposed to be decent. Designed by Tim Depavaracini I believe.
I've tried a prototype of the pre-amp. I wrote about it in the review section.
He also plans to do an 845 based kit. I don't know of any other 845 kit so this could be a first in the market place. Im quite keen to hear this one.
With the extremely high voltages of the 845 though I wouldnt attempt it myself, being an amateur bodger. You might be better sticking with a 300b kit.
The hifi collective kit can come either as a plain power amp, or have the option of an attenuator built in. I personally like it better with an active pre, like the one Nick sells.
If I was buying it and only had one source I'd get it with the attenuator, and at a later point add an active pre.
Its a nice amp, and a fun build IMO. It looks better than most kit amps - again IMO.
Theres someone on this forum thats got one (I forget who), you could ask him what he thinks of the 300b amp.
I know Nick pretty well, and Im sure he would build the amp for you for a couple of hundred quid if you asked nicely (and didnt fancy the DIY side of it too much).
An alternative is the
www.diyhifisupply.com ladyday kit. This is a monoblock 300b kit. Given that it would be shipped from America I'd personally be more tempted by a domestic kit. It's much easier if you have problems to deal locally.
Cheers
Chris