Several responses are leaning towards wood racks.
At first thought I had not considered wood as an option, more from an aesthetics standpoint than any other reason. The heavy nature of the wood tends to dominate the look and the audio pieces take second notice. The metal racks allow the audio to appear more prominent.
Unless the sound improvements were considerably better with wood then I would apt to lean towards metal or another material that is less bulky than wood.
At first thought I had not considered wood as an option, more from an aesthetics standpoint than any other reason. The heavy nature of the wood tends to dominate the look and the audio pieces take second notice. The metal racks allow the audio to appear more prominent.
Unless the sound improvements were considerably better with wood then I would apt to lean towards metal or another material that is less bulky than wood.