Hi squeak,
Yes, I looked at the Privia PX-310. I agree it has excellent action and piano sounds. My only issue is with the small built-in speakers. I played it side by side with a DGX-555, the forerunner of my YPG-625, and it sounds very pale in comparison. Through headphones, the PX-310 sounds much better. (Still not
quite as good as the DGX.

)
The P70/YPG-625 are the first really portable digitals, with acceptable action and speakers, that an out of shape middle aged man can cart around with no help. The Roland FP-2 comes close, but again, the speakers. I seriously intend to gig in small halls with the 625.
I like all in one solutions.
The demos for the DGX line are pretty bland, too. Frankly, they put far, far more effort into the demos of pricier products.
Jeffc, I think the pianos on the P70, YPG-625 and PX-310 are close enough that I'd need to play them side by side for more than 24 hours to make a decision. They are all very good.
The Privia is "tri-element" sampled, but that's a more subtle distinction than you'd think. It does NOT mean there's no difference in tone between the YPG piano sound at p vs. f.
One real difference: the PX-310 has soft and sustenuto pedal inputs; the P70 and YPGs have only a damper pedal jack.
Rick