Synthfreek, you've described my tastes exactly! I don't do much of the new stuff, but listen to the classics all the time. I managed to catch Celtic Frost on the Monotheist tour, just before the breakup. Absolutely stunning show and fantastic album - they were responsible for so much innovation in modern heavy music, the scene still hasn't absorbed all of it. Venom, Bathory, Mercyful Fate - all favorites as well. I am a real big fan of Destruction, Coroner and Bolt Thrower as well, in addition to many others. NWOBHM favorites: Praying Mantis, Samson, and anything Nicky Moore was in (from Tiger to Mammoth).
My system is also horn/tube: Klipsch La Scalas, Quicksilver Horn Monos, Cary SLP-2002, Rega Jupiter 2000, Michell Gyro SE/RB600/Goldring 1042, cabling mostly analysis plus + nordost. A balance of smoothness with enough detail and great dynamics - the combination works really well for metal.