New home theater setup

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.

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

"...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." (Nohav)

I'm stating for the record that I never recommended driving the RXV700 ALONE! I'm most definitely recommending a 5/6 channel dedicated power amp to be added to your receiver, driven from the preouts! This is clearly the best sound you'll get, if you must stay with the RXV700 (if it even has them..not sure). And, in keeping either the RXV700 (processing/switching dubties) or the old DSPA2070 (amp dubties - suggested in this case), it only makes sense to keep the RXV700, which clearly has superior, up to date processing, meaning superior detail and processing of all new digital formats, superior video swiching, etc, etc. There's no debate there. And yet, all things considered for sonic properties, IT'S STILL JUST A RECEIVER ...on it's own. I was just saying ,"if you had to", I'd stay rxv700 and add a bargan power amp avail on the used market, for dirt cheap!
To be clear, even the much heavier, near 50lb DSPA2070 - which I sold in at least 2 audio/video shops in the mid 90's - had an amplifier section that was only adequately stout, and not so refined. For an av receiver, however, driving smaller speakers, it worked nicely, sure (speakers that matched the bit cold, slightly hollow and bit upfront treble.
Keep in mind, as someone who spent litterally thousands of hours in AV stores and hi-end audio shops, my position is that NO mass manufactured AV receiver really ever offered an amp section that's been anything to brag about! Not only is/was the power section dedicated to having to not only run the speakers, but also the preamp section, the digital circuitry, power volume controls, lights, and so on! All that, and out of country made parts and cost restrictions (face it. AV receivers pack a lot of features for the bare minimum amount of profit margin for low cost!), and what suffers is the quality of the amp section!
I remember years ago, when we compared flagship Yamaha and Denon 50+lb AV receivers, on their own, vs using even modest entry level same line receivers driven by separates power amps, and the sound quality of both music and movies - driving either small or large (especiallly much better for large) speakers - WAS CLEARLY SUPERIOR USING THE LATER COMBINATION, OVER THE STANDALONE AV RECEIVERS!
So, I typically am always going to recommend not only not spending big bucks on an AV amp but, if you do have to use one, either drive small efficient bookshelves with them, or drive your speakers out to a better multi-ch amplifier for vastly superior sound!!
I eagerly dare any av enthusiest to try and take their AV receiver and compare to separates. I think you'll find the later to beat up on the appreciative sound quality and power vs what comes included in just the receiver! That's all I'm sayin.
Yes, the 2070 is too old and too out of date, processing wise. And, unless you absolutely can't come up with $200 more dollars to get better amplification to mate with it instead, then sure the 2070 will make a better amp than your 23 lb rxv700's amp section.