I plan on doing this for my band's EP. But not entirely different tones. Probably a 6505 left + 5150 right with the same settings or maybe just two different boost pedals.
I find when using the same player for rhythms with the same settings for both tracks it can "mono" out pretty easily, losing the stereo depth (but using two different players changes the tones a bit too much for my case even with the same settings. All in the hands.)
uhhh. not to be a dick, but uhh...the 6505 and the 5150 are like, the same amp design. the difference is a 6505+/5150+ vs 6505/5150. the only difference you would get is through different settings, cabs, or overdrives.