Can someone describe the sound of KEF IQ30's ?

i read reviews and they are all over the place. here is some straight advice tho.. if you must replace those polks move up an entire notch or two and buy a used set on a gon that will outperform the kef. i am basing this on the reviews i read of them and the knowledge that you can find a 1K used spkr that would open you up to a whole new level over those polks. good luck. it will be the difference between a new chevy and a small barely used bmw.

They are voiced similar to the Polks you currently have. Polk's LSi series is much warmer than the RTi/RTiA.

I'm so hesitant to buy used speakers

your polks are better than fine.

If you "must" buy some new speakers to replace your Polks, and want to stay "south" of the $500 line, then I would recommend that you take a listen to the Energy RC-10s.

Also, since you mentioned that you like the NHT Classic Threes, you might keep checking to see if your dealer is going to reduce it's price. NHT is closing it's doors on March 31, so there could be some "good sales" on their remaining speakers, as most dealers will probably be dropping the line. Kind of sad to see them go, and hopefully wiil see then (NHT) on the "other side".