There's a lot of good shit out there, and even more trash. To be honest, the best way to tell the two apart is to listen to what's available:

HiphopDX has some good mix tapes and free releases:

http://www.hiphopdx.com/index/mixtape

Thehoodinternet is loaded with hiphop mashups for white people ...

Some classics:

Blue Calx--Aphex Twin (http://www.youtube.com/watch?v=kn7Ep71lxGQ)
Sometimes--My Bloody Valentine (http://www.youtube.com/watch?v=XXKHLx-wZQQ)
Unrecorded--M83 (http://www.youtube.com/watch?v=_B6aXGFr1S8)

Salvia can be a violent, disorienting experience. Acid/shrooms/DMT won't prepare you for the kick in the nuts that Salvia delivers, especially if you're smoking a potent extract (20x or higher).

That said, if you lowdose--chew a bitter-as-fuck 5-15g quid of regular Salvia leaves--you can get an ...