I was recently going through the same assesment, but already owning both a Sony 7000 (which I was looking to replace)and a Panasonic xp-30, for 2 different TVs.
My situation may be different than yours because I also wanted the player to double as a transport for a high-end 2-channel audio set-up (you didn't mention if audio performance was important to you).
I also didn't want to spend too much--especially with HD DVD seemingly just around the corner. Also, a lot can depend on the quality of the upconversion in the TV you're using now, or will be down the road (I'll probably (??)get a projector sometime soon).
For instance, my dealer told me that with his Marantz projector, it was better to let the projector do the de-interlacing (upconversion) and to use the regular component outs, than to use the progressive scanning in the DVD player.
My answer ultimately was to purchase a Sony 7700 with Modwright upgrades. That way, when HD DVD comes I can get a less expensive one but still use the 7700 for transport duties.
That said, the XP-30 looks really good with great detail into a 32" panasonic TV using progressive scan. But to buy another for my RP TV and then junk it in a year when HD DVDs are available didn't make sense. I already have too many older DVD players taking up space.