We're in the process of testing our way through Panasonic's immense new range of TVs. So far, so impressive, but we've not yet published a review on the TH42PZ80. However, if its 70-series forebear and the new HD-Ready PX80 are any guides, it should be fine. By the by, you'll be able to check out our review in the Ultimate Guide to TV, on sale June 5th.
The projector? Don't know it. From the spec, it looks bright and and punchy, but that doesn't necessarily translate into good contrast (that's real, calibrated contrast, not a contrast ratio) or movement. I'd view it before buying. What I can recommend without equivocation is the Panasonic PT-AX200E: it's a shade more expensive, but very, very capable. Don't forget to allow for a screen, if you don't already have one.
Amp? Again, a TX-SR606 review is in the offing, but it'd a major surprise if it's anything other than capable. The '875 is, in my view, too capable for your speakers: I'd save the money and settle on the cheaper Onkyo. If that gives you the spare cash to opt for the Panasonic projector and a screen, then so much the better.
The rest? Fine. The Pioneer was and is a cracker, despite its age, the PS3 is a fine affordable Blu-ray source, and the Quads are terrific.