MC501 or MC601 or something else for B&W 802N?

I really don't have a problem with the tweeter right now. My 805N were pretty strong but I don't know why the 802N tweeter is not as upfront. In fact, I am missing a bit of midrange energy in comparison. However, the midrange clarity has improved with the three way.

I'm really considering using pro amps to biamp or going $$$$ mono blocks.

I wouldn't recommend mac with 802n's. The music seems slow and lags behind when you are listening to fast paced songs. I tried it with the mac402 and pass x350.5. The pass was a bit better but I think there should be better. Maybe burmester? I would recommend a more dynamic amp to pair up with the 802's as they are slow sounding speakers (to me).

"I'm really considering using pro amps to biamp or going $$$$ mono blocks."

Pro amps are usually much lower quality than high end amps. Bryston is an exception. Also, if you are going biamp, would it be vertical or horizontal?

Zd542 - from a thread from last year I mentioned liking the EP4000:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1349961481&read&keyw&zzbehringer

Since that time I have tried a few nice amps - Luxman 505U, MF A5, Arcam AV600, Mac6700, Exposure 2010s2, Bryston 2b, Naim Nait ii. All of them have been good or great but honestly I really like the sound of the Behringers. Noting has made my Maggie 1.7s sing at all like the Behringer.

Now I have two of them so I would be using one amp per 802N, removing the jumpers and amping each channel with it's own gain control.

In my experience, the poor image of Behringer has not been reflective of their performance. Then there's this dbt: http://www.matrixhifi.com/ENG_contenedor_ppec.htm

You should look into Hegel as well. I used to be a B&W owner, now Harbeth. Looked at integrateds for about two years and nothing came close to the Hegel H200 in my system. I found the Luxman 505u and the top of the line Marantz to be lacking. It's worth looking into. Lots of reviews out there on the Hegel H200 and H300.