Which Would You Choose?

We shouldn't call someone's system or components junk; many of us have financial or spousal constraints......and can have really fun and enjoyable systems without dropping $100,000 or more.

However I do agree that the OPs speakers are not the limiting factor, and that maybe the amp upgrade he's looking at may not bring the sonic upgrade he is looking for.

I'd dump the Monster HTS, and you didn't mention how your power looks (other than the HTS). If you have not done so I'd look at pulling 2 dedicated circuits if it's feasible (about $500, but use good cable) and 2 high quality receptacles like Furutech GTX-D(G Gold) or GTX-D(R Rhodium), or Oyaide R1. Plug your amp directly into the receptacle, and you can connect the signal components into a nice audio quality power strip/surge protector. The power upgrade will pay large dividends weather you keep your current amp, or decide to upgrade it. 

Low cost system well embedded can pass the minimal acoustic satisfaction threshold ...

I know it because i know how to do it ...

"Better" upgrade does not always means huge improvement especially if WITHOUT ANY UPGRADES you are able to control the signal/noise electrrical ratio of the room/system/house, the resonance/vibrations problem and the room acoustic with what you already have ...

People who advise to upgrade BEFORE embeddings controls implementation invite others to throw off their money...

I dont need upgrade with my 700 bucks system synergetical and well embedded ...

The BACCH filters will be my only upgrade ...Because it is an acoustic revolution ...😊

As Jetter said advising to upgrade all parts, supposed to be junks , BEFORE trying to improve the mechanical,electrical and acoustical working conditions is the wrong advice ...

The fun part of this hobby is studying and experimenting to improve hugely the end results with low cost expanse if the system is synergetical to begin with ... If it is, it is enough for experimenting ...

Be creative with what you have FIRST and give your money to your wife or children ...

By the way there was NO COMPARISON at all between the three different systems i created ( 2 speakerrs based one and an headphone one )  by controlling the mechanical,electrical and acoustical working dimension  BEFORE and AFTER ...

We must learn what to do before upgrading pursuing passively an illusion, read about acoustics which is way more than just room acoustic ...

Upgrade your speakers, keep the amp and upgrade cabling. 

Another proposing upgrades instead of studying and experimenting and learning what to do ...😉

It is like most people in this hobby know nothing save buying ...

Dont change your amplifier now save if you feel it is not synergetical at all ...

OP listen first  to someone who know about speakers :

• Your room (erik_squires)

@soix and @jeffreyw already recommended what I was going to say. I believe your best bang-for-buck upgrade may be a power conditioner.

Like you, I have a more mostest system. I dropped an AudioQuest Niagara 5000 w/ Tornado power cable into the system, and I was rewarded with better everything. Part of me was expecting no change at all, or a slight change only that wouldn’t justify the price. After that result I had, I picked up some AQ Hurricane power cables and also put a Niagara 1200 on my TV system. I was pleased with the results. I’ve played with a handful of sub 1k power conditioners and some sub 1k power cables and haven’t been impressed with the results. Another power conditioner that seems to be getting ubiquitously good results is Puritan, which is under 2k USD.

I would suggest comparing your Monster conditioner against a standard power strip to start. If you’re not hearing a difference, or if it’s just a slight difference, I bet you'll be pleasantly surprised with a dramatic improvement with a Puritan or Niagara.

And, if your results aren’t dramatic like mine were, then sure, put the money into a different component. I can’t speak to your power amp, but I’d think the NAD could be improved upon. My vote would be to consider the Holo Audio Spring or May DAC/pre’s.