Pairing of Magnepan 1.4 with Marantz SR7007

I'm pretty new to hifi (really didn't start building a quality system until the last few years and am a very budget conscious young adult paying off a mountain of student loans) and this is actually my first post on this site.  

I'm looking for some thoughts on pairing a pair of used Magnepan 1.4 speakers I recently purchased with my Marantz SR7007 receiver.  I recently came into ownership of a pair of used Magnepan 1.4 speakers for $250 locally and they appear to be in great shape.  I can't tell any signs of delamination of the wiring from the Mylar film, but I haven't taken the dust covers off of the speakers to check in detail.  I have replaced a pair of much more efficient Klipsch KF-28 floor standing speakers which I purchased open box from Best Buy with the Magnepans which I was running off of my Marantz SR7007 receiver.  I knew the sound quality and detail would instantly be better as I had heard Maggies at the local audio specialty shop in the last year.  But it is still surprising every time I start the system up and hear the difference.  Just for a reference I am mostly streaming Tidal lossless through a Audioquest Dragonfly Red or Meridian Explorer 2 DAC directly into the aux port on the Marantz.

The Magnepans are currently set at a crossover of 60 hz with the bass being picked up by a pair of entry level 8" Klipsch subwoofers.  Right now I'm trying to determine if there is really any need to consider upgrading to include an external power amplifier in this setup.  I believe the Marantz is rated at 125w into 8 ohms, but not sure if the power supply on this unit has the ability to really provide the current needed for the mangepans or not.  I so far haven't had any issues with the Marantz shutting down or showing signs of excessive heat (at least any warmer than normal).  I usually listen at moderate levels without cranking volumes too high as I am in close proximity to neighbors and conscious of protecting my hearing.

Would an external amplifier with a better power supply connected to the pre-amp outputs from the Marantz provide a significant benefit?  Would there be a significant difference between Class A/B and Class D in this application?  I know Class D technology has come a long ways, but has it gotten good enough where it can compete with Class A/B in the same price category?  How would external amplification likely manifest itself in the sound of this system?

Any suggestions on a good budget amp (new or used) that would be good for this application?  I've had a friend suggest Crown amplifiers for the good amount of power they will produce.  Other have suggested a good NAD or Rotel amp.  But not sure I'm in the market to spend $1,000+ now.

At the end of the day, I will likely enjoy these speakers for the time being on the Marantz as it really doesn't seem to be a bad combo at all.  I'm not completely sure the upgrade that might be realized would be worth the added cost if it is likely to require an additional $1,000+ investment (keeping in mind that I only paid $250 for the speakers).

Thoughts?