You are aware that you need to recallibrate your display each time you change DVD players. Most people do not do this. That may alleviate the "softness" which you are experiencing. Or it may not. You can use the AVIA setup disc or a sound and Vision callibration disc for this. Both are available at places like Best Buy and Amazon.com.
Rkuryl is right. The MPEG decoder in the RP91 is the player to beat, IMO. The RP82 has the same MPEG decoder, and has the same, slighter worse, or slightly better picture than the RP91 (depending on who you ask). Also the scaling of the RP91 is really excellent. Which is important if you have non-anamorphic discs as Rkuryl noted. The deinterlacing of the RP82 will probably be slightly better. So it really comes down to whether scaling or deinterlacing is more important to you. That, and the $200 or so price differential.
Definitely check the avsforum.com forums. Lots of videophiles hang out there!
I'd consider the Philips DVD963SA before the Q50. The 963SA is just out and is supposed to be excellent (in the same league as the Panasonic RP82). I think it's selling for $399-499 at some places.