I noticed these a few days ago. It's a very good deal, especially if you don't have any of the bits-and-pieces (charge controller, inverter).

54W is actually a useful amount of power. I wouldn't go with less than 45W for a mobile setup. It will keep all your battery-operated items (flashlights, LED lanterns, laptops, NiMH chargers, radios, cell phones, etc.) running quite nicely. Someone has thought this through.

FWIW, I have a couple of ICP panels (a 5W and a 15W). They've been out in the weather, -30C to +30C, for about three years now and have kept trickling out the precious juice.

In terms of hooking this setup in series: I'm pretty sure the panels would take it (most can take up to 10A, though check the documentation). But the charge controller that's included is only rated to 4A. So buy two setups and hook each to a big fat battery. Switch over as required.