$550 is a great price for an SX3 in any sort of decent shape.
I've had an SX3 Waterfowl 3 1/2" gun for about 7 years. Bought it used. Gun sold new for $1100+ over 10 years ago. It also got the Duratouch gooeys. Sent it back and it was returned looking like a brand new gun.
I mostly use it for turkey hunting. An Indian Creek choke tube and a Winchester Longbeard XR in #5 shot and you gotcher self one NASTY turkey machine. I put a Burris red dot on top of mine to keep POI precise my where it is maximized.
