What's a fair price for an Audio Research Reference 75?

I have recently heard from a couple guys that had bought new ARC REF160s and just couldn’t part with their REF 75’s. Once owned a lot people really just can’t part with them. 

Looks like around $5K.

The HIFiShark site has sales records of more than 20 REF 75s on US Audio Mart. Click on the "Sold/Expired" tab at near the top of the page, then click on the "Site" column heading to group the sales by where they were sold.
https://www.hifishark.com/search?q=Audio+Research+Reference+75

$5,000-5,500 in excellent condition

I got the SE version dealer demo for 5K.  Paragon is offering BRAND NEW ones that ARC dumped on them in both color choices. You might be able to snag a new one for 7K-ish.  Ive seen MANY of these for sale as HIFI SHARK bears out so not sure where your looking.

Wow, an SE for 5K? What a lucky man! 

Is it possible to upgrade a Ref 75 to a 75SE?

Yes but no idea how much it costs.

yes - upgrade can be done to run kt150 - contact greg christensen via email to the audio research customer service webmail address - he can give you up to date costs

Move it out for 4k asap.

Great amp, great used pricing as the replacement is very overpriced. 

SE version just popped up here on Audiogon for 5200 in North Carolina

$5200 in North Carolina is pick up only. Will NOT ship.