Im not sure if this helps but........
my guitar player has a H&K attacks 1x12 combo amp. IT is all solid state. the combo itself sounds awsome. It sounds like a tube amp, really it does. I have tube amps, so im not just saying it. it has a really nice break up. the clean channel is pretty good, but not like your fender would be.
ive never seen the rack mounted preamp you are talking about, but im sure if its like most preamps(for a live application), you would hook it into a the input of a power amp, then to out to your speaker cab from the power amp. for recording you may need to hook the outputs of the preamp to a DI box then to your recording console, unless there is a dedicated output on the preamp that is meant for recording then you may be able to just go from pramp to recording console.
I think it is a older model, like late 80's early 90's so it will probably sound pretty fuzzy with out speaker and amp modling for recording, just guessing. i will look at his amp next week and find a date for you if that would help in any way.
value of it, i have no idea, not even a guess. H&K's are usually expensive new.
good luck.
