I play the cello. Played pretty consistently through high school and college. I got to the point of being able to play most of the big concertos and other major repertoire pieces, albeit much more poorly than a professional would. This thread reminds me I should play more often.
No experience with "Amazon Special" cellos specifically, but I will say really cheap instruments can kill the joy of playing. You really have to work hard to get any sort of decent sound out of them. In my experience, around $2,000 was the floor for something that doesn't feel like you are fighting it. From there, $4-6k instrument feel like a big improvement, but playing my instructor's $25k+ instrument wasn't a revelation in comparison to my $5k instrument (though it was a nice improvement). May be worth renting a better instrument instead if you'd like to dabble.
Since you already play the violin, Cello shouldn't be too terribly difficult. Even though I have no formal violin training, I can pick it up and make something resembling a decent sound, especially if I put it in my lap and play it like a cello. Don't try and hold a cello like a violin though
). I've no intention of switching instruments, but I was thinking it may be fun to get a cheap one just to fool around.