Just to toss in some stuff....
What is your current workout that you are bored with?
push/pulls....splits....isos?
And what kind of circuit are you thinking about doing?
full body, or upper lower?
just curious....
If there is ever a time of the year that circuits are good for, is
now, the holiday(s) can kill ya on time/energy. Not to mention, you may actually find your gym a little lonely b/c of the holiday hustle.
Good luck nonetheless,
train hard always,
~g~