I am mainly looking for stage pianos.

Should I get the Casio PX-150 and connect it to my laptop and use the software sound samples from there to play? Surely 10 GB sound samples from my laptop will sound better than anything any digital piano has out right now, correct?

Or should I spend more (maybe $1000 to $2000 budget, what pianos would you suggest?) for a higher end digital piano with better sounds? Surely it won't sound as good as the laptop's samples right? But the digital piano won't need to have a laptop connected to it to sound good, less clutter around the piano. A convenient all-in-one solution.

What is your advice considering the above?

$1000-2000 DPs will sound better than the PX-150, but both of them still won't sound as good as outboard software pianos.

Are you actually going to use it as a stage piano (moving it back and forth?), or is it going to live at home?

The new Kawai VPC + a virtual library like Galaxy Vintage D would be an excellent combo for home piano use.

If you don't need the premium Kawai action, you can save a ton and just use the PX-150 as a controller. The privias are the best price/action quality IMO. The PX350 and PX5s are more capable as stage pianos (PX5 also offering more sounds and midi control surfaces/capability), but the actual piano sounds are the same AFAIK.

The Kawai MP6 is a very nice stage piano and midi controller as well.

What is it you want to accomplish? Do you want the keyboard for job purposes? If so, then you won't really won't need a laptop.

Do you want the keyboard for recording purposes?

I was happy using my CP300 (the big brother of the CP33) on jobs just for the piano sound.

You're going to have to give us more information. If you want to use a laptop why not just buy a midi controller?