The challenge is not elevation, it is cold. I'm not in the US but I just looked at the 8b zone and coffee will not tolerate frost. If you have a greenhouse or can grow in pots and move them somewhere warm in winter then you will be able to grow delicious coffee at any altitude. Fresh home-grown coffee is a taste sensation and out ways any other factor. If you can keep them above 32F then go for it.
I've been growing and roasting delicious coffee at 500' for over ten years. I get asked about it all the time so I decided to make some videos to document the process.