You'd save a heck of a lot of money if you just book it on the German DB rail site, if you can deal with the German. The connecting trains in Switzerland are included in the ticket, Half Fare Pass or no Half Fare Pass. I have the German Bahncard 25, which gives a further 25% reduction. Good deal all in all. For example, this Summer I did Montreux to Dusseldorf for €14.25! You'd never get a price like that booking on the Swiss SBB site!

The RailPlus seems to come free with these cards. I've got it on both mine.