I think the answer is obvious..
The quad , while quite pretty, is also nearly worthless.
The 2235 is a 30 year old near bottom line receiver.
Now, they may have given the customer $100 each against some obscenely expensive, high profit equipment, but what they really gave them was 0 for the equipment, kept the customer happy and discounted something a little.
The fact that its forgotten about in a back room should really indicate its value to them and in their mind.
I'd think $10 each.. maybe $20 on the 2235. Don't ask them to waste their time hooking it up to listen to it.. drop the $20-$30 and run. In fact, on second thought I'd say "I am willing to play with it and see if it works.. I am trying to get a little retro look in my den and these fits.. I'll take both in case one doesn't work.. How about 10 bucks (not specifying each)" My guess is he'll take it and clear his stockroom.
That would be exactly what I'd do..
Remember, your mindset is that of a collector and afficienado, their outlook is "if it isn't A/V DTS nobody would even want it.." The reality is that they are closer to the real world and the general population than we are... Try to find a "stereo" store anymore.. You'll find A/V dealers that might have a few pieces. The mass market isn't where we are at.