I don't think the czars are constitutional. In fact, I know they aren't. You can call them heads of departments if you want, but that isn't how they always operate. Some of them are under the heads of the head of the cabinet position they most closely fall under, some of them are heads of departments that didn't exist before they got their job, some of them are actually in charge of things they don't say they are by title. But the bottom line is that many of them are not, and never will be, approved by congress, and most of them have no one to answer two but the president himself.
No check, no balance; it's the same as a monarchy.
By the way, I think Obama has only just surpassed Bush in the appointment of czars, so this isn't a dem/rep thing.