I think than Mysql, and PostgreSQL, would be unlimited because are gnu/opensource databases. MatrixReseller have as unlimited the Mysql and PostgreSQL databases
Are they reliable?
I don't know if you did this already, but you can try to use the search feature of the various hosting forums out there. (I'll add webhostingtalk.com and hosthideout.com on your forums list).
You can also ask each host to provide you with uptime statistics.
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