I have a red sea reefer 170 and actually switched from running two MP10s to two Red Sea gyres. I personally like the flow from the gyre much more than the MP10s. That is just my opinion as you will definitely be trading off some of the programmable settings of the mp10 that the gyre just can't do.
One gyre is definitely enough for the red sea 170 tanks. I ended up buying two because I personally didn't like how all of my euphyllia were constantly being pushed in one direction.
I have my two gyres placed on the right and left of the 170 tank. With the reef beat app I have them set to alternate in power. So for example my left gyre will go for 20 seconds at 40% power while my right gyre is at 10%. Then they will swap. It's actually pretty cool because you can see the water turbulence shift from left to right in the tank. Also my corals aren't constantly being hit from the same side.
Note that the reverse setting is only like 10% power of the regular forward setting. So one gyre can't fully alternate the gyre direction.