From what I understand, your just looking for a pump to pump from the storage tank into the pressure tank correct? Your search will be easier if you use the keywords "booster pump" Backwoods solar and a multitude of other companies sell booster pumps. I have not purchased mine yet but Im looking heavily at the the 24 volt shurflo.
booster pumps
One thing you might not realize is most panels in the wattage your looking at, are 24 volts panels, and while it is possible to take 24 volts and charge a 12 volt battery, it requires an expensive charge controller in the 500 dollar range. The cheap ones will do 24 or 12, but the panels must match the battery bank.
I was convinced I was going to install a grundfos, but I did not. I went with a simple pump, I encourage you to check it out. I used it as a hand pump for awhile but now I use it with the 24v version of the motorized.
simple pump
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I would think you should not have to worry too much about dirt entering the pump. Most particulates will settle out in your storage tank, as long as your not pulling from the very bottom of the tank and you conserve water, there should be enough time spent in the storage tank to allow settling