You are looking at two great speakers, both of which would benefit from sn amp.upgrade. You have an Adcom GFA-5400 - that's a Nelson Pass designed 100W MOSFET that was a great amp new and is still competitive today. I'm pretty sure your Marantz has pre outs, so you're one set of interconnects away from a very workable amp setup. Now, let me toss out another speaker you should consider. A Stereophile Class A rated full-range system, the only one under $10,000 pr. The Monitor Audio Silver 300-7s. I have a lot of respect for both the 2ce and the Sonnettos, but the MAs are simply a better value. Range, dynamics, transparecy, they are the complete package. If you're not a Stereophile fan, then consider these: the 2021-2022 EISA Award for Best Product in the Floorstanding Loudspeakers category, the 2021-2022 Hi-Fi News Best Value Floorstanding Speaker award, and the 2021-2022 Hi-Fi News Outstanding Product award. Yeah, they're that good. And with 90dB + sensitivity, your Adcom is plenty of power. At $3250 per pair $1750 less than the Sonetto, that leaves enough to start to consider what your next step might be.