A 2 speed pump is great for affordable day in and day out circulation while still having a high speed for the spa and the pool sweep.
I really don't recommend them on water features because they gobble up relay spaces.

On your DE -vs- multi cartridge filter question I'd suggest the FNS 60 or Clean and Clear 520 over the StaRite product. Those StaRite filters are indeed great but don't use industry standard grids or replacement elements.

See ya,
Kelly