I don't know about the ME-50, but I've had and used the GT-6 for over two years now and love it. Never had a problem. I run mine through effects loop 1 of a Carvin V3 100 watt Head into a 412 Legacy cab loaded with Vintage 30's. This set up sounds great and I searched a long time for my Tone, some would call me and do call me a Tone freak. These things are built like a tank, very solid. I've seen them on e-bay for under $200.00. Good luck and let me know how it works out.
Merry Rockin Christmas, Bill Kelley