I'm on track to finishing my home renovation and figured now is a good time to start thinking about a receiver. I recently purchased the NHT "Absolute 5.1 Surround Package" and I will be adding additional speakers over time. Browsing NHT's site I came across Marantz, and researching Marantz I came to discover this Denon AVR. As you may be able to tell, I am fairly new to this whole audio/video world, but after a few weeks of reading through this entire thread, among others, I came to a few conclusions/realizations.
1. My viewing room is far from ideal. While the space itself is fairly compact (~15' x 20'), I have an open floor plan, so the effective area is much larger (~25' x 51').
2. My speaker choice might make filling the space difficult as they might not be efficient enough. (I am still trying to figure out how specs translate to efficiency.....)
My question is - would the Denon 4520 be a good choice to help deliver the power I need with no external amps? I want a fairly immersive experience, and while I know that is subjective I hope that the objective is somewhat clear.
While it's true that the NHT's are of below average sensitivity (only 86dB for the front towers), I think you will be OK in terms of amp power given the size of your space. With the speakers, the open floor plan is less of an issue, it's more about the absolute distance to the listener. It does seem like the couch is pretty far back in that diagram, if you could pull it forward a bit it would help in that respect.
That said, it depends how loud you want to play. If you are looking for full on movie theater ass kicking volume, then the cheapest route is more efficient speakers, not a more expensive receiver. The important thing to understand is that the dB scale is logarithmic -- 10dB increase requires TEN TIMES as much power. That works out to approximately double the power for a 3dB increase. So switching from 86dB speakers to 89dB sensitivity speakers is like doubling your amplifier's power.
The open plan and the subsequent huge volume is much more relevant for the SUBWOOFER which has to pressurize the space. I would make sure to budget for a really nice sub (or two) in your plans. $1K on subwoofer(s) would be the minimum IMHO to match the size of the space and the quality of the speakers/receiver you are looking at.
If it helps clear the budget, I would recommend going with the 4311CI instead of the 4520CI, as it should offer the same sound quality but at a pretty hefty discount. You lose a couple of newer features but unless you care about 4K or the matrix HDMI switch for another zone it's nothing of consequence.