My impressions after burning in the MA Platinum 300 speakers for about 30 hours with my Benchmark LA4/AHB2 pre/power:
Compared with the Cantons 7k. Both have a wide sound stage but the Platinums have a deeper one. Q Acoustics Concept 500 sound stage is still wider (if my memory is still reliable

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The instruments and voices focus are mostly the same.
The bass on the Platinums is better. Goes deeper and feels more "tuned" and detailed than the on 7k.
The Platinums seems to have no issues with room integration. The bass reflex ports are small and looks like the speaker behaves pretty close to a sealed box bafle. On the Cantons this was a little trickier.
Mids and treble feels a little more defined on the Platinums than the Cantons. Both speakers sound very alike on my room FR-wise, however. Both sound natural and real but the Platinums have a smoother presentation. I have the impression that the drivers on the Platinums are better integrated as the FR transitions are flawless and silk smooth. With some live music like Pink Floyd's Pulse album the guitars on the Platinums where breathtaking. I was amazed how real this live concert sounds on the Platinums. I believe the Platinums have the absolute best rendition of that album that I have never heard.
Detail-wise even as the Platinums are smoother they are also more detailed and textured. So they are just "perfect".
Final comment: I feel that I could live with both speakers on my room, they are both great. They are both Reference-grade speakers. They don't have any significant flaws. The Cantons have a small hump on the midbass and a couple dBs higher tweeter level and that's it. Both details are easily solved using an sponge and compensating with using a lower toe-in angle. However, the Platinums have an edge for not having those and for taking detail, bass deeph and smoothess to a higher level. They are like a 7k "version 2.0" where everything that the 7k does great the Platinums take it to an "amazing" level. Is the price difference justified? No it is not. They are maybe 20% better than the Cantons but cost almost 3 times. MA Platinums are speakers for someone that has to have the "best" because it can, not because is needed. But this is not because the MAs don't have the merit, it is because the Canton's value is outstanding.