You just need an equalizer. You've spent a lot of money on what amounts to equalization. Anything that "changes the sound" between the source and the amplifier is just that.
As for the Vista amp, maybe the reason the midrange sounds fuller is because it's cutting off the bass:
The same review notes that the Spark is only capable of 9 watts(!) at 4 ohms, which means it has no kind of current capacity for any impedance dips. If you didn't have already efficient speakers, that amp would be an absolute dog.
You can probably get something like the JDS Subjective EQ (
https://jdslabs.com/product/subjective3/) and pair that with the Emotiva and make slight adjustments to get the sound contour you prefer, with plenty of power and current to play the Lore's as loud as you want when the urge strikes.