Thank you joker, you are always great help.
Regarding sound signature column I would probably try to add all key-words if one doesn't fit. maybe not strictly sound signature related but few components that make the set belong to some group or make it unique. Then in extended search people could choose key words they are interested in like clarity, enhanced bass, wide stage, etc. You could allow to make negative choices as well, like show me all but bassy and siblant.
Or you could just use a symbol like V, U, - as appropriate...
And combinations of properties would indicate that it's somewhere between. V + F would be somewhere between V-shaped and Flat. Easy as pie... OR? Whatever you come up with I'm sure that it will be awesome. Just like this thread and the interactive guide.