No not collectible particularly, but very useful amps, with a good clean sound and an immense amount of clean headroom. Take pedals well. I have one which I lend out to people who've left an amp for repair and lack a spare; they are often surprised how useful it is.
The original firm went out of business, but the designer and original manufacturer, Steward Ward, still supports the amps and will sell you parts and advise on repairs. Here's his website:
Award Session Website. Welcome to award-session.com [AwardSession Website], guitar amps and music amplifiers
I guess 'bi-fet preamp' refers to the presence of fets in the TL071/072s in there.