With no speckling and feathered feet you don't have a Speckled Sussex. I do not know of any Sussex variety with feathered feet but there are Sussex varieties that are not speckled. I'd say the chances are you have either another breed or a mixed breed.
Well, I was not prepared to find out we have a mutt rooster today. We love him and think he is beautiful anyway. This does change my plans to get a Speckeled Sussex hen and hatch chicks. Hmmm plam B. I could contact who I bought him from, however, they are an hour away. Am I going to drive an hour for a replacement chick? He represents 1/5 of my flock.
Any other thoughts on a possible breed? Maybe a Brahama and Copper Maran mix??