Ryan Paevey, Andrew Walker and those previously stated are all good. I am a fan of Victor Webster, Wes Brown and Warren Christie, too. Chris McNally and the other newbie on When Calls the Heart. I think about the only actress Ryan Paevey has really shown chemistry with is Taylor Cole though.
If I had to chose one it would be Victor Webster.
ETA: Unfortunately Warren Christie isn't in much on Hallmark but they recently reran "The Color of Rain" which is why he came to mind.