When buying a used edge of any model, ask them to print you 2 11.75 inch high squares, use cobalt blue, print the first one with a 50% half tone and the second a linear fade from 90% to 0%. Tell them to clean the printhead first and use good quality clean 2 mil vinyl.
What you are looking for is a burnt pixel (quite obvious, its a thin white line that does not print) or in the fade a dark section that interrupts a smooth fade, this indicates a bad clutch.
I don't know about your country, but it looks a touch expensive. I do like the FX, but it would be cool if you found one bundled with an enVision plotter, they are a bit faster and make some really cool musical sounds for you, lol!
I always have used Edges on my website, no FX's currently though.
Craig