there's a good discussion here. but it really depends on how much you wnt to spend... i have heard the garriton and , for the money , it's good.
I submitted a piece of music to someone which would have been approved for upload to a site if it wasn't for a 'synth' sound to some of the classical software instruments. Is it possible to produce more realistic sounds with the existing midi notes with third party software such as Vienna Symphony Library?
I looked at this software but wasn't sure which package (and there seems to be numerous options) was the right one for my purposes.