New home theater setup

I need some input here. What do you think about the 2 receiver approach?

I think your idea will work. It wouldn't be my first choice though. I would eliminate the old receiver from the set-up, and add a good power amp. Chances are the seperate amp will be much better than the old receiver is. Most, receivers don't have the greatest amp section. There are a few I have heard that are very good though. (I don't know if your old Yammy is one of them) I would put the old unit in my bedroom, or a 2nd system somewhere. If that really isnt an option, try your idea and see how you like it. You have nothing but some lost time if you don't like it. Good luck.

Regardless of size of speakers, cross em at 80hz, and make sure they're placed well for 80hz coupling in the room, and with sub, from the seats. Regardless of what receiver you use, or amp for that matter, you'll get better dynamics from those speakers if you just drive em above 80hz, I promise u!
Also, DITCH THE DSPA2070! It's time for that piece to go, and the amp section in that unit is still nowhere near as good as better dedicated multich amps! (that included the dspa3090's amp sections, which were not so great). For $200-350 used you can pickup a number of superior sounding 5 or 6 channel amps, from Parasound, Rotel, Adcom, etc. All of these blow your receiver's amp sections in the dust, no contest!
If you must keep you latest receiver, this is the route I'd go, as long as you got he preouts. OTherwise, you might consider upgrading units to more beef?

Why? 100w vs 90w. None sense. I believe the new receiver would smoke your old one and then some.

Maybe it's just my ears, but my Matrix 3s driven by the old Yamaha amp seemed fuller, while the new receiver sounds somewhat thin. I have to admit I haven't put carpet in the room yet or worked to "tune" the system in... If you've ever picked up a 2070...it's a bear. Weighs something like 46 lbs. And while I'm sure there isn't a linear relationship between weight and power, that kind of solid build has to count for something.