The original NuVo Music Port (NV-MP) was exactly this... It's a combination of a NuVoNet adapter (serial to NuVoNet) and the Autonomic Controls Mirage software. No longer sold, but they do pop up on eBay.
Easier to find (and a current, supported product) would be to get just the NuVoNet adapter (NV-NNA) by itself (same adapter, just no software bundle) and buy a copy of CasaTunes - which has very similar functionality. My only gripe with CasaTunes is the lack of native Pandora support, but they do have Airplay support, so you can get there - but without metadata / control. You can also buy a copy of the Mirage software from Autonomic, which does support Pandora, but hasn't been updated in quite a while (as they've been focused on their music server products).
By far the easiest, but more expensive, path is to just get the NuVo MPS4 server (or the Elite, which supports network-shared libraries), which has everything done for you.