Biamping vs. Biwiring Pass Labs

Looking at the specs the X600 looks pretty much as powerful as a X350 but in mono. Would there be any advantage of using 2 X350s instead of 2 X600s and using one channel to drive the mid and highs, and the other to drive the bass (Nautilus 801s)? So you're using one per speaker but bi-amping...

I've done this with several speakers Maggie 3.6r, Revel Studio and Salon. The benefits to biamping are many. Biamping with two X350s would be better than 1 pair of X600. The ultimate would be 4 X600s in a vertical biamped configuration. When I did this with ML #436 it sounded incredible and the bass. . . look out. Things you never heard just pop out. By biamping you're going to a whole new level.
To hook up your amps, you'll need a pair of high quality Y-adaptors. Don't fall for the you'll need two separate pair of interconnects routine as my understanding it that inside your preamp the line outs are not wired separetely but split to the connector.
With this configuration your 891s out to sing!
Thanks Sgr, I think 4 X600s is a bit too pricey for now, but the 2 X350s does sound tempting, I think it'll cost be a little more than the X600s but it does allow me to do it in stages. The Pass X1 has a 'tape out' this the same as the output? So could I run interconnects from that and the output? The Y adaptor seems a bit fishy to me I'd rather do it seperately if possible.

Thanks a lot for your advice...
The tape output is a fixed line level signal making it unaffected by the volume control. Therefore it will not be useful in this configuration.
I would call Peter Perkins at Pass (530)367-3690 and ask. You might even get Nelson on the phone, as he answers it sometimes.

The reason I suggest calling is it's my understanding that Nelson Pass thinks of mono-blocks as the way to amplify & a stereo amp is for convenience. Like anything audio, YMMV.