If you have quality carts that are in good shape and you're still unhappy with water quality you could try using polyquat 60% to see if it helps filter some of the smaller bits.

An oversized sand filter will filter better than a smaller one (as long as it can be backwashed). With sand you can also polish the water with a little DE to catch finer bits than the sand can by itself.

Some parts of California have water use issues. Is water use limited where you live? Sand filters require occasional backwash - dumping water which must be replaced.