I already had the IIIs, and was simply so curious about the IVs after the positive reviews that I just had to grab a pair. I noted someplace else that the IVs are far more sophisticated in their assembly, and compared to my IIIs, the finish is much better. My IIIs are the "Capitol Records 75th Anniversary" edition with an "ebony" sort of deep purple very thin (scrapes off easily) finish over some veneer. So...The IVs initially did what they’re supposed to do, deeper bass, new midrange tone. But there’s the rub...the mid horn on the 2006 designed IIIs is a far more complex (weird design with a the titanium driver blowing into a long pointy tube with 4 holes in the base where the diaphragm connects, but hey...it works) design with a titanium driver, and the poly driver horn on the IVs is a far simpler and shallower "bolted to the flare" design with a small phase plug...the mids on the IVs weren’t making me smile...even after a couple of months of break-in, certain tones (especially acoustic piano) on recordings I’m very familiar with sort of barked...upper mids. An acceptable sound if used with somebody else’s gear maybe, but I demand that speakers I live with make me instantly satisfied at all times or they’re outta here...the IVs are beautiful, well made speakers that just didn’t work for my ears, and they looked so good I figured a quick sale would ensue...it did (I priced them fairly though, and figured my small loss was an "extended audition fee.") The new owner seems to like ’em. My IIIs are likely to stick around, but I’m now curious about ZU stuff and a pair of Omen 2 "dirty weekends" will be in my room by Friday...it’s a risk of 100 bucks for a 2 month audition...what could go wrong?