Hey, i'm glad you enjoyed my map! You'll be happy to know that I am currentlyl working on two maps; an abstract-themed map along side other members of Nipper's forum, including Nipper himself. I'll keep details on that map under wraps for now.
The other map i'm making you'll appreciate a lot. It's the sequel for nightmare, cs_nightmare. This map will feature randomly occuring events. Hopefully that will scare the pants off some people.
As for your sound request, here's a list of where the looped sounds (that didn't come from the default HL2 list, or HL2: Episode 1) came from:
Radio in room with flying beds, past blood hall: Candyman Theme - The theme song from the Candyman movie.
Creepy mirror bathroom in T spawn: Hallucination Voices - sound clip from the Max Payne nightmare sequence.
City street above street light with rotating lights: Max Payne Nightmare - The main music from the Max Payne game nightmare sequence.
Secret Dance Club - Song #1: Madness Club Song - This song is from a flash animation called "Madness Combat". Check out http://www.madnesscombat.com/episodes.php to see them.
Secret Dance Club - Song #2: Remix of Sonic 3 & Knuckles level song "Flying Battery Zone". Taken from ocremix.org, home of countless game remixes. (Since you like Sonic, I suggest checking out remixes from several Sonic games. Many of them are quite good!)
Secret Dance Club - Song #3: This clip is from a song a friend of mine composed. It's not available anywhere.