Combining 2 channel audio and home theatre

@audiotroy Okay i've found a few Integrated Amp's with built in streamer that supports tidal. Thanks for the suggestion! i'll definitely consider this. 

But how about my first step? if i just connect a 2 channel Power Amp to my AVR, will it have a noticeable good difference in the audio quality? Since, through this method, i’ll be giving a good quality dedicated power amp to power my L/R rather than the low grade ones from my AVR. Basically, through this method i’ll be turning my AVR into a pre amp. I'm just confused that if the pre amp function in Denon AVR is good enough and match that of an Integrated stereo amp? 

and one more question, adding an integrated amp or a Power amp brings major difference in the audio quality? that leads to my previous question, is the preamp function in an AVR as good as the ones from an Integrated stereo amp. 

Sorry for asking too much questions, I'm pretty new to this. 

Not sure of your budget but my dealer carries the Gato DIA-250 S integrated. Excellent DAC's w/digital inputs. 250wpc 8 ohms and 500 wpc into 4 ohms.. Has HT passthrough. $3500.

That is a very capable AVR, perhaps others are not looking it up

https://usa.denon.com/en-us/shop/receivers/avrx3700h#divSubscribe

As for a dedicated amp(s), separates being better, come on, in a dedicated listening system, in a bigger space, bigger home theater, yes, but that darn good AVR in your space is plenty good enough IMO.

Considering both 5.1 and 2 channel (I do a heck of a lot of this, every day, for many years, using my Sony AVR, blu-ray; cable; youTube; netflix; amazon prime; hulu; viki; music shows Voice/X Factor/Songland/ occasionally streaming Pandora while doing something else ... Sound of my small Home Theater is very important. Both 5.1 and 2 channel. I also have dedicated 2 channel system elsewhere, that's dedicated separates.

You need to improve the speakers, add center, rear surround, and self-powered sub.

Your speakers are efficient, however they dip down to 4 and occasionally 2 ohms, which can be difficult for some amps.

IF you have enough volume, and no obvious distortion, and no weirdness from the AVR, then the Denon is dealing with the 4/2 ohm load.

A. add a center channel speaker (definitely needed for 5.1, off for 2 channel).

Any surround coding records/separates designated sounds for the center channel output. Those sounds DO NOT exist in front l/r, thus a center channel speaker is imperative. I love this very compact Bose center, easy to locate just below the image

https://www.ebay.com/i/233696110070?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&am...

B. Add small rear surround speakers. In a small room, I have used small speakers on their backs, shooting up, using the space between the back of the sofa and wall behind like a horn. There's no real bass, small ones decent efficiency will do. Again, any surround mode, these frequencies/sounds DO NOT exist in the front, center, or sub channels.

C. add a self powered sub to your nice but small bass limited front l/r speakers. And hook the sub up so that it is still working in 2 channel mode which can be tricky.

Self-Powered Sub will accomplish 3 things:

1. take the low bass signals away from the amp, the self powered sub will amplify those frequencies (adjustable crossover needed somewhere, typically in the sub)

2. take the low bass requirement away from the front l/r speakers, so they don't distort trying to make low bass.

3. Their mids and highs will sound terrific when not in a self-made cloud of not so great low bass.

Surprisingly, MUCH Video sounds better in 2 channel mode, even though the cable box/AVR chooses to use a surround mode. Learn how to go from dolby 5.1 to 2 channel to compare, stay there or back to dolby 5.1

IF it was a bigger room, I would either change your main speakers, or add a stereo pair of front firing directional self powered subs, to preserve bass directionality, especially 2 channel.

if i just connect a 2 channel Power Amp to my AVR, will it have a noticeable good difference in the audio quality?

A high quality integrated amp with HT bypass or power amp definitely will be an improvement, but for the budget of $700, I doubt you can find one with noticeable good difference in the audio quality.

Your Triangle BRO3 is not that hard to drive, for two channel playback, the Denon AVR should be able to do the job well. My suggestion is spend your money on room treatment or add a 2nd subwoofer to improve bass response.

´´ NAD D3045 Hybrid Digital DAC amplifier ´´ is in your price range.
I think you do not need the pre amp section of an integrated amp.
Tidal uses ´´ Leedh Processing ´´ and it is better with amplifier only.
You Denon AV  ´´ pre out ´´ will be connected to  the amp.´´  input ´´only.

Room treatment is half of the sound.