Ignore if you've already done this....
If possible, can you post a pic of your mains position. It might pay dividends to look at changing their position slightly. Speaker setup is king.
An error of even a couple of degrees when toeing in speakers can make a huge difference in timing, coherence, spatial imaging and percieved treble smoothness (sweetness).
Buy a line laser and set up your mains pefectly matching in distance and angle to your mlp. Best upgrade you can do for about $100. Period. A measuring tape, line laser, level and masking tape will get you there.
Then, pour more money into finer components. (If need be of course.
)
