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Klipsch makes a great loudspeaker but if your concentrating on HT, you should use the same series of speakers for your front stage. The RTi8 prices at Fry's are pretty smoking and would be a perfect match to the CSi3.
The RTi8 as a surround speaker is overkill and if you want to ease the pain on your wallet the R or Monitor series would be a good option. Since you don't want to mount anything, I would suggest the Monitor50. As far as pricing goes, I'm not sure which wil be cheaper but the MSRP on the Monitor50 is lower. The Monitor series isn't a timbre match to the RTi, but it's closer than the R series sonically....and the R series is older. In the end, buy what you get the best deal on.
Start over? Nah. I think the RTi8 and CSi3 is a great front stage in regards to Polk speakers.
What else could you do? If you save some money on surrounds, pick up a CSi5 for the center channel. It's more robust and handles dialogue more in-line with the RTi8/10/12.
If there's anything else I can assist you on, feel free to ask....even if you don't go with Polk. Either way, good luck!
Mark