DrAzzy:
I use AMC7140's to drive those kind of panels off 12~15v at constant current. The dropout on the AMC7140 can get very low - and they'd dirt cheap.
The AMC7140 is only rated for 700mA, so you're suggesting that instead of running six panels in parallel (which is what I'd planned - 12v @ 3A), you're suggesting I run the panels in series (70v @ 500mA)