Classical and Ambient

I'm don't know about classical, but from the sounds of it, Dark Ambient would be right up your street. Check out Lustmord, Raison D'etre, Northaunt and Convalescence to start with.
To be honest I'm more of a regular ambient fan, so if you're interested I can drop some band recs for that too.
 
"Dark" classical?

Start with Beethoven, then some Verdi for contrast, then get through your Brahms and Schumann and Schubert, then try Paganini for contrast, then get into Bruckner.

You will be floored, if you make it. Most don't.
 
If he wants really dark classical he must get into more modern stuff, beethoven or verdi is hardly dark.
Try some later Shostakovich,Ligeti, Allan Petterson, Bartok's String quartets....and of course Arvo Pärt, if you want Minimalism with lots of ambience, then he is the man.
 
Beethoven is a lot darker than any of the modern stuff, in part because it does not attempt a single mood. I don't find the recent stuff that fulfilling, sorry!
 
Check out Gorecki's Symphony No 3 (Symphony of Sorrowful Songs).
The Swan of Tuonela by Sibelius.
Ligeti's Requiem.
Anything by Chopin.
Rachmaninov's Isle of the Dead.
Firebird by Stravinsky.
I also wouldn't describe Beethoven as particularly dark, although his piano sonatas are worth checking out.

Killbot's dark ambient recs are on the money.

Check out Elend for a unique cross-ver band between classical, metal, ambient and industrial/noise.
 
Ambient bands (lots of them verge on other genres like electronic/post-rock/glitch etc):

Boards of Canada
M83
Tangerine Dream
Ulver - 'Perdition City' and 'Teachings In Silence'
Devin Townsend - 'The Hummer'
Atrium Carceri (Much 'darker' than the bands above. Kinda like what you hear in lotsa horror movies)
Helios
Sigur Ros
Portal
Datach'i

Classical/Soundtracks etc:

Franz List
Ludovico Einaudi
Michael Nyman
Philip Glass
Thomas Newman
Modest Petrovich Mussorgsky
Gustav Holst
Cliff Eidelman
Arturo Toscanini
Akira Yamaoka (Silent Hill soundtrack ;D)
Pyotr Ilyich Tchaikovsky
Dargaard (dark neo-classical/ambient stuff)
 
Any more recomendations, I have always wanted to explore classical but do not know where to start and have not been able to get any feedback or suggestions until coming back here recently. I would say I would like to start with some of the dark epic atmospheric stuff, probably newer by reading some comments in various threads.

not to thread jack the original poster but I know how to search and am also bookmarking this by posting in it as well and you may get some suggestions.