Not Muddy, perhaps a bit bass-heavy but not bad or over the top (I feel a little sound wave massage in my left shin now at times). I keep the HU EQ flat because is mine there is no reason to tweak it. The highs are sparkly and fine with the new tweat and getting a little imaging even from the better coax in the rears. If I want more or less bass, can easily dial it in with the dedicated sub gain control knob.
COuld yours have something to do with the retro fit if I am remembering correctly you moved yours from one rig to another right?
I hope you get it dialed in to your liking.
JC
P.S. - As for songs to test it, I just try to listen to a variety of songs (different genres whether to my liking and not) and from a variety of sources (Radio, USB, XM, CD, etc.) taking into account the virtues and limitations of each source and genre. For instance I really like Lithium 33 on XM but as previously talked about it's highly compressed... still sounds way better then stock. I listen to Hawks game Saturday on FM talk to make sure voice radio wasn't obnoxious, I took usb key out of wife's car with NOW! pop music that my kids like to listen to in order to test wide variety of treble/bass pop music from 320kbps rips and finally for the best most pristine, I listened to my remastered TOTD, Stone Temple Pilots, U2, Nirvana etc. all of which are more my style. I wasn't just one song or a best song, it's all of this over past two days and very few things were disagreeable (mostly R&B/Hiphop/Dance type of stuff That's I'll never listen to anyway... no offense to those who like that stuff).