While I have heard several of the Linn DSMs. I never did any analytical or comparative listening. But more from experience with Linn and other reputable high end brands. They are carefully priced on sound. Dealers and users are quickly going to suss out useless upgrades. Linn would not want that… it would endanger their whole strategy.
As one appreciates the sound quality over time of a component, what may first seem like small differences are much more profound when listening day in and day out. I have never failed to experience appropriate sonic improvement from different levels of cost investment from audiophile grade equipment. Mid-fi and budget… totally different story.
As an example, I have had both an ARC REF 160s stereo amp and a set of REF 160m monoblocks for many months (exact same design, just one in one chassis and the other in two)… $12K difference in cost. When I first switched them I could detect and describe some differences.
After months with the monoblocks in my system I switched back. The difference was very profound and dramatic… but explained by the same words I used originally.
After listening for 700 hours with all kinds of music I got to fully appreciate the strengths and differences, with all sorts of different musics… textures, dynamics… etc. Absolutely no question in my mind that the mono blocks are worth $12K more now that I fully understand their capability. Unless you are a pro, constantly listing to different high end equipment it takes a lot of time to really grok a piece of equipment.
While it may seem like a big outlay at the beginning, two years, four years and more in retrospect it seems like a small difference. Unless you are a contant trading equipment kind of guy, I would go for the better one. It will also, kill the constant wonder if maybe you should have got the good one.
Now if you are a guy ridden with buyers remorse after every purchase. Then I have no idea what to recommend… i guess good choice you are not buying multiple components that you can feel regrets over each component.