Hi,
I play most of my music by Apple lossless files through ipod classic with NuForce ipod DAC.
The quality of the source media is the most important part. Are you sure the files are really lossless, I mean originall lossless such as imported from CD via iTune with the proper setting. I think the itune default setting is not lossless when ripping CD, you have to manually set it.
1) I think my towers put out very pleasant mellow sound with a rich soundstage but I really want more definition and clarity, esp. in high range. I'm not sure if the general mushiness of my sound is more a product of my speakers or my receiver. Advice?
I bet you are right, if your Cambrideg Audio towers are in good working condition, they should sound very good. If it sounds mushy, it is more likely the quality of your audio files and/or your receiver if you play it loud in a larger room. That pioneer AVR can probably do a decent job if only driving the pair of tower but not a very loud level as it will run out of gas trying to push those not too easy to drive tower speakers.
Have you tried playing some CDs that you are familiar with?
2) even after calibrating speakers and boosting center channel, dialogue is still very low and hard to hear relative to everything else. Should I consider just using stereo or stereo focus through my towers and skip/disconnect center speaker?
What's the specs of those BIC center speakers, and did you also try disengaging MCCAC? A quick way to find out if the issue is more related to the speaker or the receiver, you could swap out the center with one of the Cambridge Soundworks tower II.
