Cagney: Regarding Morin, Dowzak and Spade and their pro potential, I would rate them in this order: Dowzak, Morin, Spade.
Dowzak's size alone will make him a very attractive pro prospect. As we saw from this past draft, NHL teams can't seem to get enough of 6'5"-6'6" dmen. Dowzak has a pro frame already. As he grows into his body and improves his coordination, strength and power I expect his speed, quickness and agility to improve. I'd like to see him play with more of an edge but I get the feeling it's not in his personality to play that way. He's a good bet to go in the first or second round of his NHL draft.
Morin reminds me somewhat of Danny Richmond. He's a strong skater who loves to join the attack from behind. He has very good offensive instincts. Although I didn't see Morin play much this past season, I saw him a lot when he played in Syracuse and at the Prospects Tourneys in Toronto. Based on these viewings, his play on the defensive side of the puck needs a ton of work. His defensive zone coverage reminds me of Tim Gleason. He doesn't seem to process information very quickly and often seems confused and unsure of where he should be depending on the situation. From a coaching standpoint, he is a guy who I would have firmly entrenched on the end of the bench in any tight game and whom I would have a hard time trusting in an important game. However, with his offensive upside I think some NHL team will adopt the mindset that they can teach him how to play the game without the puck and select him in round 3 or 4.
Of the three players you asked about, Spade is the guy I have seen the most. I have seen Spade play on 27 different occasions in the past two seasons with Georgetown and Barrie. To be honest with you, very little I have seen from Spade impresses me. He's an average skater and puckhandler at best who has no offensive upside whatsover. I'm not sold on his defensive game either. Many scouts I have discussed Spade with seem to think he's a very good defensive dman. I think they take a look at his stats and think "he doesn't do much offensively and he's got a good reputation so he must be good defensively."
In the seven games I saw him play against Mississauga in the playoffs he looked lost, scared, and completely void of confidence. He saw very little ice time early in the series and almost none by the end. He may surprise me and take his game to another level with more ice time next year or his weaknesses may be exposed for everyone to see. He's been well hyped in the province of Ontario (some people were actually suggesting he could have been the first pick in the OHL draft last year) but I've never seen anything to suggest he's a bluechip prospect. At best, I think he's midround pick, even though he's a late 87'.
For what it's worth, the best 87' American dman I have seen is Adam Abraham from Mississauga. He probably won't be a first or second round NHL pick due to his size, but he's very intelligent on both sides of the puck and plays with the poise of a 4 year OHL vet.