Has anyone commenting on this thread actually HEARD a pair, fully restored, set up correctly? I've had a perfect pair of these for a couple of years now and I have to say ...as a dealer (no I have no affiliation with the seller) I've had a lot of GREAT speakers come and go. My imperial 9's are not going anywhere. I run them with 15 watt tube mono blocks in a medium sized livingroom and they are stunning sounding. They dig extremely deep and do so very cleanly, the mids are smooth and non fatiguing, and the highs are good for cheesey cone tweeters.
Speakers I've had the pleasure of owning or working on and listening to extensively.
The majority of the ADS, KLH, Advent, and Boston lines, Carver amazing, Dahlquist DQ10, Dahlquist dq8, JBL 4311, 4312, L100, C70, EPI 50 all the way through 500 (still a huge fan of EPI), many epicure, AR, Magnat, RtR (the good older stuff like 100d, 600d, hpr12 etc) VMPS tower II and II SE, yamaha ns1000, ns670, all of the pioneer HPM including the 200's, Design Acoustics, many of The POLK stuff up to the SDA's, All of the Infinity Quantum line and most of the RS line, Fried, KEF ....ETC the list goes on.
I've had my imperial 9's to a few audio meets (NOT FUN to haul around....) and along with the VMPS's and carved amazings, the Imperial 9's were crowd favorites. I've owned all of the rest of the Imperial line and they are pretty ho hum compared to the early production 9's.
Why did I choose to keep my 9's over all the rest?
1) After spending extensive time with a lot of different speakers, I found I could listen to my 9's for hours on end with no listening fatigue. Yes, the tweeters so not extend much past 18khz, but neither do the beloved EPI airsprings.
2) They are VERY EFFICIENT. Anything I have tube wise will drive them to wall flexing levels on the occasion that it may be called for.
3) they truely have quite clean and flat bass down to about 20hz, -3db at about 18hz. I dislike subwoofers and have never needed one with these.
Your milage may vary. I'm not claiming them to be the world's best speakers...and everyone's tastes are different, but set up correctly they won't dissappoint. You may find those cheesey blue dyed drivers embarrassing many much 'better' speakers.
As for the OP, $600 is a lot to pay for a pair needing woofers. I can tell you that the woofers are unique to the Imperial 9 and may take some time to find. I have seen these sell for as little as $300 and as much as $1500... Nobody wants to ship them. They are quite rare so if you are looking for a set you sort of have to take what you can get.