I personally think your team looks very good, I can't see your team not being a serious contender. With that said I defiantly hang on to Perreault, as he's a proven player and will put up decent points, and should continue to get better. I think Gerbe is worth keeping as well as he will be able to contriubte to your team right away, and I think he's capable of putting more points than he's put up thus far in his career.
On defense you look quite good, I wouldn't consider dropping any of your current D for any of those available.
Brett Ritchie is an interesting player, I like his potential, but I don't think you have anyone on your roster I would drop for him, same thing applies to Kabanov.
I like JT Brown, I doubt he'll become the best player of those who are available, but I think he's worth keeping an eye on, as I think can bring immediate help to your team. I would add him in place of Colborne.