What Percentage Off Would You Expect to Discount For Open Box Amp with Blemish

The dealer should pay you to take it.

too many unknowns to answer:
what's overall demand on this brand/model - easy sell?How significant is the blemish? - way too vagueWhen its discontinued - is it now obsolete or suddenly in demand?
You e my point. Careful with the generalizations above. There are products that become classics the day they are discontinued. In fact there are chips that are MD that i pay a premium for....

Note: I am presuming an impersonal store moving inventory. I prefer to deal with individuals on a friendlier basis :)  Sounds like a larger store. It's still pandemic time. If you really want it, forget about the Memorial Day. Doesn't matter. Go to the highest level person you see and say: I'll pay $1995 for that right now. They'll tell you it's impossible. Don't move one inch off your price. Talk to the manager, the manager's manager. Don't add one cent. When you are talking to the GM of the store, that's the first time you budge. If it's over $2500, say "I can't even start negotiating with you, because that's way too high." If it's under $2500, ask them "Is that the absolute 100% best you can do?" They'll probably lower it. Then and only then, offer to split the difference, and you'll get it for maybe $2100-$2200. 

@corelli @itsjustme then

I’ve always thought 10-12% off to be the norm discount on prime products.I know this isn’t set in stone. But what is "normal" ?

Here’s the question I asked. What is so vague about that? Not a poor question. Here’s the answer Then if 10-12% off were the typical norm, then it should follow automatically that a blemished product demands more discount. Its speculation but not blind or without enough info.

Perhaps the biggest problem is that most just read the header and don't read the body. And thats why it seems vague. 

Recognizing that 40% off is likely to be dealer cost, you got to be reasonable as the dealer is entitled to eat too. 
The blemish is relevant. Is it something the dealer is willing to replace. Ie- a marred faceplate where the dealer could get a new one from the factory? 
Instead of asking for a discount make an affirmative offer of a specific dollar amount.