you could use a mag24 which would give you a little more like 900gph at 12 feet head. I calculated your head loss with this pump using 1-1/2" pvc
with a ballvalve, three 90 degree fittings, and 4 unions in case you want to have access to the pipe at any time. (plus the 10 ft horizontal, which doesn't really alter the head loss).
This is your cheapest option, other pumps would be overkill and would need to be throttled back quite a bit to end up at 800gph.
The ampmaster 2100, would be another choice, but is probably double the price and has 2" outlets.