Hey MS,

Good luck with your new toy.

Are you using those stock ceramic resistors for your higher frequency?
If so, the best thing you can do is to spend $3-4 each on premium resistors.

If you can give us detailed information on the speaker positioning,
Such as:
*Your room size
*Distance to the front wall, sides, your favorite chair.

I'm sure some planar freaks here can help you out, but mostly trust your ears.

Best wishes,
JRA