Best cheap used Samsung phone?

Hey guys, recently I got a used Samsung Solstice II with charger off ebay for around $45 shipped. I like it, but as I've been reading it does have some problems, in particular shutting off randomly. I have experienced this a few times myself.

Now, I have 30 days to return this if I wish. More like 27 days now.

So, now I have to consider if I want to return it and get a different phone. I like this phone, but it does have problems. I would be willing to try a different Samsung phone.

For reasons that would just bore you, I have to get a phone without a contract. Therefore, I'm looking at used phones for around $50. $100 at the most.

Used Samsung phones in this price range that I know of are the Eternity, Eternity 2, Impression... I'm sure there are others.

What do you guys think is the best bet?