SiMSiN

Hi All, I am planning to upgrade from 5.1 to 7.2 When i initially purchased my setup I got a sweet deal on a Klispch gear, so all my speakers are Klipsch. I am using an Onkyo-NR-709 2 x RF-82, 2 x RS42 & RC62 Klipsch SW-112 Do I need to get the same sub to the one I already have? Klipsch SW-112 If not what would you recommend in the used or the new? I would also be looking to add 2 more speakers. What would you recommend in the used or the new? Thanks you