a flat plate of MDF with a round flat plate of more that spins I'm not surprised will resonate with the speakers.
Which is the modern belt drive turntable that hangs the motor from rubber bands for isolation? Is that one of the Pro-Ject models?
Rega. Loved their tonearms- thought the rest of the turntables were pretty disposable.
I think Pro-Ject also did that on a few models.
IMHO, if you want the really good gear that Pro-Ject makes- buy a Music Hall. Better performance for the money, IMHO. The mmf5.3 is $1199, and a lot of $10K turntables DON'T sound as good.
For cheaper models- it's still hard to beat a Denon DP300F. For just over $400, you get a automatic start and stop, a good arm, good suspension and a removable headshell. Drop a better cartridge on it (many people use the Ortofon 2M Red or 2M Blue), and it will sound as good as anything short of the mmf5.3, IME.
Regards,
Gordon.

