This recommendation is close to "hardcore" classical, but is classical music written, primarily, for the guitar (some has been transcribed from music written for other instruments); thus, even though it is classical music, it probably will be "different" sounding than the classical music familiar to you. With all that said, here are two recommendations...
Christopher Parkening & David Brandon "Virtuoso Duets" EMI CDC 7 49406 2 This CD contains music from the renaissance through a piece written in 1989 (23 songs). A lot of the music is from Spain, much of it based on native folk songs. There are a few "hardcore" classical numbers. The last selection, Andrew York's "Evening Dance" wirten in 1989 is, alone, worth the price of the CD.
My second selection may not be available on CD, but I'll mention it anyway. If you want to hear, in my opinion, the greatest (classical) guitar duo in history, then seek out Ida Presti and Alexandre Lagoya -- their music is certainly very classical, but you will never hear two (acoustic) guitars sound more beautiful. Of their short recording career (Ida Presti died of an illness), I would recommend "Spanish Music For Two Guitars". Spanish music is the essence of classical guitar and this LP (CD?) contains 8 selections, one by Fernano Sor, a romantic composer.
I hope you get a chance to hear these recordings.
