If you want to see a fantastic S gauge layout using AM track go to tuveson.com. Carl also has details on the website of how he modified all his AM turnouts. If you have AM modify the turnouts for scale wheels be sure to verify highrail equipment will still work with them. The reason is your Legacy Berkshires have highrail wheels. AM rail is .148 high. I believe the AM turnouts have what in HO is called an insulfrog design so frog juicers are not required.
As mentioned above Fox valley makes .138 rail flex track and #5 turnouts. Purchase the high rail #5's and add shims. They will then work with both scale and high rail wheels. The FV turnouts have an insulated metal frog. That allows them to be left as unpowered, or if some engines stall on the frogs they can be powered with frog juicers.