squarepusher Music/IDM necessities

I want to buy some music before SOPA may come into reality and I want to know some IDM/Musical essentials

What are some albums that are a MUST HAVE? Excluding Rdj/Ae/BoC of course as I have all that.

Corrently buying Squarepusher's discog and might get a bit of VS (blasphemy I know, buying VS...)

I'd say mu-ziq's Lunatic Harness and Plaid's Rest Proof Clockwork and Not For Threes and some old Black Dog stuff.

Maybe some Clark too.

At least that's what got me into this kind of stuff.

What is SOPA by the way?