A TeeBird and a Comet. If you can't consistently throw these discs dead straight with your forehand, you need work on your forehand, not another disc.
Super fast discs (Nukes, Forces, Flicks, Wraiths) will net you distance gains and a ton of bad habits. If you really want to up your distance, do it right. I have friends that throw super fast discs, and I'm rarely too far behind them in the fairway throwing TBs (I just switched to PDs very recently) and Comets. I can get TBs out to ~325' and still fade at the end of their flight (the distance potential of this disc is enormous). My Comets fly to 250'-275'.
I don't mean to be mean, but I remember where I was during my early years of playing. Buy slower discs and learn to throw them correctly. If someone were nice enough to give me the advice I just gave you (no matter how little I wanted to hear it), it would have saved me a bunch of "huck and pray that my Force/Flick/Wraith/Nuke doesn't OAT itself into the ground five feet in front of me" throws and untold strokes.
My .02