Hi. First, as to the Andra IIs, this is not a hard to drive speaker, and in fact the manufacturer's recommendation is 100 watts per channel, unlike the original Andras, which ate power. I biwire them with McIntosh 501s, which have about 5 times the recommended power, and that is vastly more than needed for any conceivable purpose, in any likely room. Before I got rid of my old amps, Classe CAM-300s, I tried biamping, first with the Macs on top, and then the Classes, and there was no gain, and maybe some loss, as to clarity, soundstage, etc. I really think, unless you already have the Pass amps, that you are spending a lot where there isn't any great likelihood of gain.
On the other subject, if you are getting an original X-01, the upgrade to Limited is a vast improvement over the original, for $1200, and the warranty is extended. The Limited is far warmer and richer than, but equally as detailed as the original, without any of the etched quality which sometimes made the original a bit offputting. If you've heard the Limited and still want to get it, or the original, modified, fine. But if you haven't, and are just going on the difference in sound between the original X-01 and the after-market modification, you're going blind--aurally, that is. But to each his own, of course.
On the other subject, if you are getting an original X-01, the upgrade to Limited is a vast improvement over the original, for $1200, and the warranty is extended. The Limited is far warmer and richer than, but equally as detailed as the original, without any of the etched quality which sometimes made the original a bit offputting. If you've heard the Limited and still want to get it, or the original, modified, fine. But if you haven't, and are just going on the difference in sound between the original X-01 and the after-market modification, you're going blind--aurally, that is. But to each his own, of course.