i dont think there is really much of an underground scene as far as trance is concerned .
Its a pretty popular and widely spread style of music now and seeing how a great deal of people that are producing it all stick to the same well known and overly used types of sounds and arrangements there isnt much out there that you could really say is underground, underground to me being something that is experimenting in some way and not playing it safe by making sure its wideley appealable.
I wouldnt say im into trance music these days but i still keep tabs on whats about out of curiosity and if i was going to name one producer who id consider to be experimenting within the genre itd be james holden.
Im not sure what hes been upto of late but not to long ago he was coming out with some quite deep and thoughtful music which sat in the more thoughtful area of trance.
Ozgur can seems to be another producer who stands out as being more musical then the rest of the bunch.
Infact i dont belive it to be a case of whos underground and whos commercial in regards to trance now, the nature of the genre has become commercial from its mass appeal but within that predictability there are a handful of people starting to change the rules and providing unexpected moments in there music which are a rare thing nowadays.