Definitely get an AC20. The tank is so long that the Red Sea Nano won't cut it. You can turn the flow down some on the AC20, which is nice. No complaints on this end. It's just a $10 price difference and is well worth it.
ADA Aquasoil, if it's new/uncycled, will create an ammonia spike. Fluval Shrimp Stratum is just plain old clay/dirt that doesn't do much.