The $50 I picked up is a MFRT 640B. I mainly bought it for the cords, but it works so well that I have used it a bit already. I replaced the 120v cord on my big unit with the cord from a computer monitor. Perfect fit.
I have been very happy with the operation of my other unit. I have had it for a few years and probably ran it for a total of about 300 days in that time.
I had to replace a board right after getting it, but that was stupidity from a friend. NEVER RUN ON 12V WITH A BATTERY CHARGER HOOKED UP!! It fries the board rather quickly.