Make them fit. Those are the type of speaker you get, figure out the details later, as your wife frowns and shakes her head.
They are now 30 years old. $10K new. I don't think speakers hold value as a vintage car-even if they are immaculate. Maybe there are a few exceptions?
Value is a subjective thing, like the rest of audio.
http://www.ebay.com/bhp/infinity-irs
Ebay listings are all over the place. I wouldn't open my wallet for over $5K....I think 5K is a stretch.