I'd go for old Candlemass first. The classics are "Epicus Doomicus Metallicus" and "Nightfall". For Solitude Aeturnus I'd say "Through The Darkest Hour". It's their darkest.
Same here, I've always like SA more. The new album should be arriving at the beginning of next week! I can't wait! I ordered the digipak with the 10-minute-long bonus track!