Biamping, yes or no?

Edwyun,

"But, generally, passive XOs have a more deleterious effect that active XOs."

Do you mean an external passive xover or just the ones inside the speaker? Either way, what kind of deleterious effects are you referring to? I'm not saying that you are wrong, I'd just like to know.

The chances of doing something like that and having it sound good is almost 0. If you want to upgrade, why not just go with the M180's by themselves? That would probably sound a lot better.

"You might get a second W4S STP/SE preamp, and use one preamp each for left and right channels. Use the balance control on the preamps to fine-tune the balance of low and high pass. Use one stereo amp each for left and right channels. You'd have to use Y-splitters on interconnects from sources to preamps."

No offence at all, but I disagree. The preamp is so vital to good sound, you would be far better off upgrading to whatever you can get for 2x the price of the W4S, instead of buying 2 of them. Same thing for the amp. I think you would have much better results if you just upgraded to 1 really good stereo amp or a pair of mono's. There are a lot of technical issues you have to deal with when you biamp. For example, you will almost certainly need to get an active xover. Just putting something like that into your system can do more damage to sound quality than the extra amp(s) can provide from the biamp in the first place.