if you are doing a 5.1 than you want either the rs-42's or 52's depending on budget. you only want to use the rb-35's if you are doing a 7.1 and you are using them as your rear speaker (and also if you are a little ways off the back wall).
i also agree to get the rs-52's over the 42's if money allows. it's not a big deal, you can always up the gain to those speakers. as far as rears or surrounds go, you can mix and match them because so little info and voice go to those you won't notice a difference. (at least that is what klipsch tech support told me).
RF-7s Horn & Crossover Upgrade - RC-7 Horn & Crossover Upgrade - RS-42 (4ea) - Onkyo 805 - LG 50" Plasma - Emotiva LPA-1 - Toshiba HD-A3 - Playstation 3 -eD A2-300 - Furman Elite 20pfi - Custom ET center - All custom power cables - Harmony 720