What case do you have at the moment?
Depending on what you are running just changing case alone may not make much difference. It could be your current fan configuration or just your PC is a hot runner.
Number one thing to remember, if it is stable and not throttling then the PC is fine. Your 3700+ is ok to run at 65deg+ without damage for 12 years, thats what AMD say, as long as it is stable I would not worry and save the money.
If your having to knock back your overclocks from in the winter, then maybe you do need more cooling; but as long as it is stable and not throttling then AMD and the component manufacturers say it is fine at those temperatures.
Just be careful not to get caught up in the low temperature trap, yes it is nice but a PC is fine in the 60deg case temp region.
Just depends if you also want a new case, or if your trying tog et your rig stable again.
currently my CPU is idling @ 30 but Case is 37 PWU is 48....
So you have low temperatures, asuming your on air and NOTHING to worry about.
Add 30 to them and yes, you would have to then worry, but that low in this heat is good!