Either the Parasound Halo A21 or the NAD M22 or the Rotel RB-1582 Mkii are great power amps for the money. You can never go wrong with either of them. Try to have in-home demo of all those amps if possible and hook those amps up to your Polk LSIM 707 speakers. You will have to hear them on your speakers and decide from there which amp sounds better on your speakers. Those three are solid good sounding amps esp for the money. I would not get the Emotiva if I were you. Emotiva isn't on the same level of audio performance or sound quality as the other three amps.

But in order to get really good sound quality of your stereo music playbacks you will have to get better preamp and DAC/streamer than your Denon receiver. I suggest you get a stereo preamp with built-in DAC and has a HT bypass or passthrough feature. It will make a world difference sonically than using the built-in preamp and DAC on your Denon receiver for music playbacks. So you can connect the preamp out for front L&R channels of your Denon receiver to the Aux analog audio input or HT bypass input on the stereo preamp. And you can connect your computer or Sonos or NAS or your home network or whatever it is to a PC USB input on the stereo preamp in order to stream Tidal. And connect the stereo preamp to the power amp that you are going to get. So when listening to music or streaming on Tidal you simply just turn on the stereo preamp and the power amp and you don't need to even turn on the Denon receiver. And when you want to watch movies or use for home theater you turn on the Denon receiver, stereo preamp & power amp and you control the volume from your Denon receiver for movies or HT. But when listening to music or streaming music on Tidal you control the volume on the stereo preamp.

I would recommend the following stereo preamp with onboard DAC :
* Rotel RC-1590 stereo preamp with DAC. It's a stellar preamp and has very good DAC. Has PC USB DAC input on the back as well as front USB input port on the front for IOS mobile devices. One of its Aux analog audio input can be configured as unity gain for HT bypass or passthrough input so when you select this input the volume is automatically disabled. You can set the volume setting at 80 for this input and it allows you to save the setting so every time you select this input the volume is automatically fixed at 80. The unity gain volume set is 80.
And you run a pair of rca analog cables from your Denon receiver's pre-out for front L&R channels to this Aux analog input on the Rotel preamp. And whenever you want to use your Denon receiver for HT or movie playbacks you will control the volume on your Denon receiver. Make sure you set the tone control to bypass.
And you connect your computer or Sonos or NAS or home network to the Rotel's PC USB input port on the back of the Rotel preamp. And you control the volume and everything on the Rotel preamp. You music playbacks will sound way better than using a built-in preamp and DAC in your Denon receiver. This Rotel RC-1590 preamp retails for $1800.

* NAD M22 digital preamp/DAC. You will do the same with this preamp. But I think the analog inputs on this preamp cannot be configured for HT bypass or passthrough and I've heard from other people that the preamp will digitize its analog inputs, so if that's the case it won't work then.

* Parasound Halo P7 preamp with onboard DAC. You will do the same process.

Hope this helps.

IMO the Rotel is by far the best-sounding amp of the ones you have listed.

The Marantz MM7025 might be the best bet for you, though. It has plenty of power, sounds very good and is only $795, which is a steal. That's the way I would go, personally.

I think Audio Advisor has them in stock.

IMO the Rotel RB-1582 MKii is by far a better amplifier than the Marantz MM7025. More musical, quieter and has lot more power, clean power than the Marantz. Different leagues in terms of audio performance. I think those Polk LSIM 707 deserves better amplification than the Marantz MM7025 can provide. I've heard the LSIM707 before and they are pretty good speakers and being the top of the line of Polk Audio and they need quite a bit of power in order to shine or sound its best.

Or you can get a stereo intergrated amp that has HT bypass or passthrough and use that for your stereo listening to music eg Tidal, etc. I recommend the Rotel RA-1592 integrated ($2500). You can set its Aux analog audio input as unity gain for HT bypass and save the setting for that input like I discussed above with the Rotel RC-1590 stereo preamp. The RA-1592 is a stellar integrated amp and very musical one too. It is basically the Rotel RC-1590 preamp + RB-1582 MKii power amp put in a single chassis. The RA-1592 has same DAC as the RC-1590 preamp. It outputs 200 wpc into 8ohms.

My other recommendation would be the Musical Fidelity M6Si integrated amp. It is a spectacular integrated amp and sounded very very good and is rated at 220 wpc. But I'm not sure if the MF M6Si has a HT bypass mode or feature or one of its Aux analog input can be set as HT bypass like the one found on the Rotel.

According to this very helpful list, yes, the Musical Fidelity M6Si integrated does have HT bypass.

http://audiophile.no/en/articles-tests-reviews/item/426-amplifiers-with-processor-input

I have the same problem in the past, at the very end, I run them separately. most AV amp sounds thin and hollow, they all class D amp. once I got a separate DAC and Rotel power amp, it's a lot better. but a separate power amp is a good starting power, Rotel would be my pick too!