I was thinking the same thing (that's what Celine sounds like
) but seriously room treatments wouldn't normally help with something like that. I'm not a big Celine Dion fan at the best of times but I wasn't real impressed the few times I heard her albums played on a good stereo, ie I didn't think the recordings were real good.
The one downside of a real accurate speaker is that if the recording has a hard edge you will hear it loud and clear. The M3s, 40s and 50s are supposed to be a bit more tolerant in that regard.
Do you hear this effect on all Celine's albums or just a few albums/tracks ? If just some, it might be worth posting the details so someone else on the board who has the album can comment re: whether they hear the same thing.