Uhm... No, I'm not saying that scrambled image and screaming rules out monitor refresh limitation. Your case may be different from jakes.
In Jakes case, it died all of sudden while working. So, assuming he was running in the right refresh in the first place, it could have been that his pixel clock just went kaputz. However, pixel clocks don't necessarily work or don't work. My experience suggests that they can fail at higher rez but still work at lower rez. So, if you your monitor fails at a higher rez, you may still salvage it for use at lower rez.
You should definitely not tax your monitor at a higher refresh rate if it doesn't support it! From your post, it's unclear whether that high refresh is supported by your monitor (anyways it doesn't now), if it isn't don't go there. Yes, possibly your monitor may have at one supported the higher refresh, but now does not.
Quality is better than name brand, even regarding beloved AMD.