It's difficult to know what may be causing the noises, but since the noise appears to be temperature related, your suspicion of bushing related issues is what I would suspect as well. This may be especially true if you live in the northern east coast where you have harsh winters.

As for what to replace - I would try lubricating the rear sway bar bushings with appropriate lubricant to see if the noise characteristics change. This may be all you need.

Let us know if this works.

OK, my 2009 R56 Non-Turbo Coupe has 137K miles.  The rear suspension is making all kinds of noises on roads that are not perfect and especially with the colder temperatures outside.  Sounds like bushings.
What should I just start ordering to prepare for a fun filled weekend tearing everything apart?  
Any past experiences would be appreciated.
Thanks