Well, if you mean a particular sound/genre by "classical guitar," then I can't be of any help! But if you mean, a piece of classical music written for guitar, then that Salut für Caudwell piece by Helmut Lachenmann for two guitars is very fine. I can't think of anything for guitars that I enjoy more. Plus, if you get this, you'll have Gran Torso, too, for string quartet, which is just about the coolest thing I know for string quartet.
Too bad that sweet two guitar concerto by Santorsola hasn't been reissued for cd. Or just played anew, on cd. I couldn't find any listing for it, anyway. If anyone else knows of a copy out there, I'd love to know about it.