What do you recommend to raise the hackles in the back of my neck?

Hope you can watch "grudge" if you have not watched it yet, it has very a different sound effect which will really scare you out...try it if you havnt seen it yet

end of the line, you might need to search for it but its really good, also try hatchet or seed those are two very good slasher movies.

Alien is always a good cult classic. Anything Ridley Scott did because he uses a lot of background sound to set the scene, over music.

Night of the Living Dead (B/W)
Brahm Stoker's Dracula
28 Days Later
Jaws (Another cult classic lol)
House of 1000 Corpses/Devil's Rejects
Rob Zombie's Halloween
Rosemary's Baby
Any of the Saw flicks
Hostel
The Fly (Jeff Goldblum)
Silence of the Lambs

For surround sound purposes, Halloween (the original, I haven't seen Rob Zombie's remake) is great. The only sound that The Shape/Michael Meyers makes is heavy breathing and it comes out so much better - and creepier - in surround sound. It really helps to set the mood

A couple of more recent ones that I think would be good are Darkness Falls (from 2003 with Emma Caulfield, because there has been more than one in recent years) and Darkness with Anna Paquin. There are a lot of soft and loud contrasts in both movies that should really come through well in your surround sound, I think.

And High Tension, which is a French horror film that's a couple of years old (2005). I looked it up on Amazon because I honestly cannot remember if it was dubbed or subtitled and it looks like there are both versions available. It's pretty intense and should also be fairly effective on the surround sound system.