I have a 60 gallon tank. I have 6 GF. Previouslyl I had a Rena xP2 and an AC 70. This pulled 600 gph. Today I splurged and added another AC110. This makes my filtration at 1100 gph as the 110 pulls 500 gph.

Am I guilty of overkill? Is this much filtration good or unnessary?

I wouldn't consider it to be overkill, as long as the current isn't too strong for your gf. If they can swim about and also rest comfortably without struggling, then it should be fine. Better to have too much than too little, right?

Watch your fish for a while, and see if they are tossed around, like Jenny said.

I always have a spot in the tank where I have some sort of ornament, mostly a terra cotta pot resting on its side, to break up any current. Some fish will ignore it and swim happily about, while others use the pot to rest behind it every now and then. Put a few smooth river rocks around it, and it looks actually pretty cool. An arrangement of any plants or ornaments you might be using at the moment works just as well. Put them in a group, and the fish will use it as a resting spot.