Well, I have a pair of S38's and am extremely pleased with the sound quality. Without a subwoofer, DVD playback is still thoroughly enjoyable with crisp vocals and deep mellow bass(LotR is...amusing

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To my untrained ear, musical quality with rock/techno/acoustic/classical was excellent.
I picked up my 38's for about $320 shipped , can't really see a reason you'd "need" to spend the extra cash on the 310's.
I'm running low buck,PC DVD to a 20" monitor, audio handled by a hercules fortissimo to an amplified Fosgate DSL Two. Not an expert by any means, but man - you wanted opinions.
Good luck,
Greg