You said that listening to Arcturus or Borknagar would spoil you, so I'm recommending that you become spoiled by purchasing some of their albums. You won't regret it, I'll tell you that much.
However, if you just want Arcturus' symphonic black metal stuff, try not to get their recent albums (though I would still highly recommend that you get them). But all Borknagar is a must.
He plays a mean bass for Dimmu Borgir and does clean vocals for that band. He is also the current vocalist for Arcturus, Lamented Souls and Code. However, his greatest work was with Borknagar in which he handled bass and growl/clean vox.