One thing I have noticed with P3. I see far less of that phenomenon than I did with P2. It may have a fair bit to do with the GTX280. I think the additional 512meg of memory on the card helps alleviate it quite a bit, along I'm sure, with a bunch of optimizing from the Winder. I also experimented with Pol's modified TrackIR curve while filiming this and because it's far more sensitive than the one I'm used to, the panning rate is much faster. The faster you pan, the quicker the card has to load and process textures. Mostly a matter of not turning your head as much, or turning it more gradually with a more sensitive curve.
One thing I do like about the more aggressive curve is I don't wake up with a sore neck in the morning.....lol.
You should be able to push that 8400 up to 3.6 with very little effort. Anything much more than that with that processor and you'll see diminished returns from what I've read. I'd try for 3.5 at the very least, but if it blows up.......you know the drill.....lol.
Cheers Mate,
Parky