It appears at least 2 corners of my '06 are squeaking with about 70k miles. All 4 shocks are still firm.
Is it most likely the suspension bushings need replacing or the springs?

Hi! Guess you have the offset issue - when you have negative offset, load on the chassis increases (especially at the corners) and it wears out faster. That's why you hear the creaking, squeaking and so on. Of course, I'm not guru in suspension-related issues. But here I fond one interesting source, that contains good range of accessories and short instruction that might be very helpful. I've bought mine from http://www.carid.com/custom-wheels.html There is also a video panel on the right hand, that explains general role of the offset - I love'em for that!))) Moreover, when you buy wheels from them, you should contact the manager and he, in his turn, contacts manufacturer in order to find more accurate choise. In other words, only thing you need to is to specify car's model:)