Hi Les, welcome.
What size Klipsch are you coming from? My opinion is that some floorstanders provide a bigger, fuller soundstage. If that is what you are used to, then going to much smaller boxes might leave you feeling a little empty. Likewise, if you've been listening to La Scala's or something for the last 20 years, you're going to have a distinctive frame of reference.
The Axiom tweeters are great - very clear, neutral and transparent. But if you are used to the sound of horn tweeters at high volumes, even the allegedly-bright Axiom "sound" may not make you feel happy. Personally, I long ago owned and recently auditioned Klipsch speakers, and I really like how smooth the Axioms sound in comparison.
Most folks around here will probably recommend the M22's as your front mains if you are looking specifically for a bookshelf. Oh, people adore the M3 and they are by all accounts a wonderful little speaker. However, since you already wisely plan on a SVS PB1-ISD, the somewhat flatter frequency response of the M22 might be a better match.
I'd be remiss if I did not tell you how much I love my M60's. I am very, very satisfied.
I've not heard the QS4's, but I love my QS8's. They are a bit bigger box, so might go a touch lower. This may not be necessary for you. I spent the extra $ on them for a couple reasons; first, I did not want to have a case of the "what ifs" and second, if I get involved in 5.1 channel music (DVD-A/SACD), I wanted to have the surrounds be a bit more full-range-capable. I did NOT want to have direct-radiating surround speakers, because I mostly view movies and liked the flexible placement of the QS surrounds.
Have you considered just keeping your Klipsch mains and getting a VP150 to see if the timbre match is adequate?
I don't think ANYBODY is going to like the idea of using QS8's as main front speakers. They are great surrounds, though.
Talk to the folks at Axiom. They will steer you right.
