Is this a crazy idea.

IMO, I don't see why it wouldn't be doable. I wouldn't recommend eliminating the center channel (just my personal preference). But hey, give it a shot. Good luck to you!

It depends on what 4-channel matrix circuits the quad receiver can do. What kind of receiver is it?

I think it would be better to use an analog Dolby ProLogic processor set to phantom mode (it sends the center channel mix equally to the two front speakers). But you may be able to achieve similar results with the receiver depending on what matrices it can do and how much control it offers in channel balance and time delay.

If it doesn't quite do it for you, I have a Shure Dolby ProLogic outboard unit. It was state of the art in 1994 and sold for $1000 back then, but I would of course let it go for *MUCH* cheaper today.

Problem: It will never be as dynamic and 3 dimmensional if you're NOT USING an outboard DD/DTS pre/pro! Processing DD/DTS movies in your dvd player, and passing the info out analog to a preamp (which is what you're doing), never works as well, overall! It's just to flat sounding, and not enough snap and punch to the sound. That's my findings.
Basically, I never encourage trying to re-invent the wheel here. But audiophiles just keep on cutting corners with HT systems, trying full range passive setups all around, bypassing processors, avoiding bass managment and subwoofers all together--and they always tend to think they're onto some "hot-ticket" approach!
Yeah, no.
Anyway, you could tinker, but I think you'll find what I'm saying. good luck