Recommendations for an Amp/Preamp combo excellent musically and very reliable

@mllc , what you describe certainly sounds like a SS amp paired with a tube Pre is what you need, as many prior postings have picked up on.

My amp recommendation is easy = CODA.

Many fine tube preamps have already been mentioned (Allnic - Aric Audio - Backert Labs - Conrad Johnson - Don Sachs - Linear Tube Audio & Spatial Audio), along with a few that have not been mentioned, such as BAT or Herron Audio. So, this is where you must decide which one offers the best combination of price - performance - looks - etc.

Good luck in your search!

Now that the PMG series is coming out, the PS Audio BHK preamp and BHK 300, mono blocks have become very affordable.  They both have tube front ends so you can tube roll and change the sound to your liking.  I’ve had mine about a year now and unless something drops into my lap, I plan on keeping these for quite a while.

All the best.

+++++ on Pass-Labs electronics. !  I have an XP-22 preamp and XA30.8 stereo amp and have had several First-Watt amplifiers.  They're "bullet-proof" and have a reputation for quality and especially reliability.  They also have great sound quality.   

Of all the amps I have paired with Maggies, including two different 300 WpC Codas, none have paired better than Parasound’s A21 and JC5. The Codas were not nearly as good at driving those current hungry panels. The Codas are great amps for conventional cone speakers, but otherwise it’s night/day when compared to the Parasounds. 

One truth I learned while owning Maggies is there is really no such thing as providing them too much reserve power. The higher the power the better. Class D power does not apply however, they need high current Class A/B. For 3.7s, I would want no less than 500 WPC into 4 ohms as a starting point. Ideally, you want an amp that can put out over 1kW during transient peaks. Maggies driven with lesser power sound like completely different speakers. 
 

I have a similar set up with 3.7i's and REL subs.  I bought used Pass XA 60.8 amps about 5 years ago, leave them on 24/7 and love the sound.  I have had 3 Allnic pre-amps and the Allnic house sound includes a strong holographic element.  The L8000 DHT is sublime with the 3.7i's.  Currently using the DHT pre-amp from a Lamipzator Goldengate DAC.  There is something magical with DHT's and 3.7i's.

There is a point at higher volume levels where the sound changes and loses its liquid character.  It is at a point of high SPL where I would only be listening to a single track or part of a track and not a playlist.  I am not sure if it is the amp running out of juice or it is a room effect/interaction.  I have a large room but one wall is mostly glass doors and windows.