Not a deal I would consider at all.
I would be more inclined to buy at least 700w of decent CE UL TUV listed chinese panels for the $700 and use the change to buy a few Ghurd controllers to dump the excess. A 700 watt dump is not a big deal, but a 70A solar controller (12v) is an expense that needn't be surmounted at this stage.
You'll do better than the 400 watts with any super controller, and do much better on poor solar days..... for a mill, square area is the measure of power available, and the same holds true for solar..... every photon counts, and area is the key.
You can also get cheeky and put some biased to the east, and some biased to the west and spread the power more evenly through the day.
.................oztules