Go ahead and try and find the Karajan DG 2 CD of Bruckner's 8th Symphony - just imagine the symphony to be the musical equivalent of a novel. Bruckner's symphonies/novels tend to be long and dense, with lots of dynamic range and extremes (pianissimos to fortissimos, slow to fast). Someone else you may enjoy is Gustav Mahler, whose symphonies are even longer! Check out your local library; check out your local used CD music stores... good luck!
Simon
Simon