Nooks

I have a 5.1 Bose single cube surround sound system that I am upgrading. I am really close to pulling the trigger and purchasing a Klipsch Reference Series line of speakers. I don't know much about speakers, audio, or home theater, so this is all very new to me. My knowledge solely consists of what i've heard in stores and what i've read online in the past week. Anyway, thought i would come here and get some advice. I am looking at getting this set-up: RF82 - $499/piece RC52 - $299 RS42 - $225 RW10 - $499 I listened to this setup at the store and it sounded GREAT. felt like i was in a movie theater. However, the more research i have done makes me question the mismatching of the different speakers. Is this really going to be a big deal? I would appreciate some advice on this. Also, are these good speakers for the price, or would you recommend a different Klipsch series? Finally, the guy at the store recommended I upgrade my receiver. I currently have a Sony STR-DE825 that I bought in 1998. The specs on this receiver is as follows: 100W x5 Channels - Dolby Digital - 4 Audio inputs/ 1 Audio output - 4 Video inputs/ 3 Video outputs - 3 Optical digital inputs/ 1 Optical digital output/ 1 Coaxial digital input The guy at the store recommended i get the Yamaha RXV661 receiver. Do I need to upgrade receivers? Is the Yamaha RXV661 the one you would recommend? They have it priced at $479.00. Thank you very much for your advice.