Controllers for about 5 years now.

Can't answer the other parts, BUT, I'd get at least one up from the 6, On my 32 watt panel, I use the Sunsaver 20.

While I was bringing the boat back around Fla a few years ago, my controller quit working. Called Morning star, and the guy worked me through looking at my unit. Explained how to read the serial nos. HE decided it was still under warranty ( by a month) and arranged to drop ship me a new unit to an address ahead of me so I could replace the unit- HIS decision, no charge.

So what ever you decide- be aware they (Morningstar) seem really concerned about the stuff they make, and stand behind it, at least in my case.