If the Ulf’s are so much better than the DI it begs the question what is wrong with the DI?
I have had three sizes of ATC - the bookshelf 20 (6 " woofer), the 100 (12") and the larger 150 (15") and they all sound very much the same just more dynamics/SPL and bass extension as you go larger. I would not think of it as an engineering achievement when different "engineered" models of speaker sound radically different - it begs the question which design is correct and does the designer follow engineering principles or just "experiment" and cobble a product together from what parts are readily available.
I advise to be wary. I would listen first - a big difference suggests you may prefer one over the other but how to know which one will be your personal preferred one without an audition. If one model hits it out of the park for you then it is hardly likely the other one will work unless it sounds very much the same (which the manufacturer has said it doesn’t.)
I have had three sizes of ATC - the bookshelf 20 (6 " woofer), the 100 (12") and the larger 150 (15") and they all sound very much the same just more dynamics/SPL and bass extension as you go larger. I would not think of it as an engineering achievement when different "engineered" models of speaker sound radically different - it begs the question which design is correct and does the designer follow engineering principles or just "experiment" and cobble a product together from what parts are readily available.
I advise to be wary. I would listen first - a big difference suggests you may prefer one over the other but how to know which one will be your personal preferred one without an audition. If one model hits it out of the park for you then it is hardly likely the other one will work unless it sounds very much the same (which the manufacturer has said it doesn’t.)