It is also a fact that a given amplifier brand will have synergy with certain speaker brands, and sound like crap with others. For instance, Parasound Halo amps have a house sound that is on the warm side somewhat, and therefore would not be a good match with a warm sounding speaker brand like Vandersteen. Unless one likes a rolled off top end.
I have a pair of Totem Rainmaker speakers, and when I got them was warned that my Nad C375BEE was not a good match. They were right, I decided to keep the speakers and acquire a different amp/preamp combination.
Anyway, whichever speakers chosen, the amp/pre need to compliment them. For Magnepan, I’m sure googling specific models would help find what amps owners have had success with. A subwoofer might be a good option here, so a preamp that will crossover the main speakers and send the lows to the sub would be the way to go. Hsu Research(an internet direct brand) has great subwoofers for under $1000. Look at the ULS-15.
Then there are cable options. Cable effects are real. Stay away from stranded wire in all of the cables. Solid core based cables do less harm to the signal. Audioquest are good but get expensive. If one can do a package deal, savings can be had for sure. One can get an amazing system for under $10,000, no need to consider $20,000 components as the OP mentioned.