I must have been in a bad mood with my earlier posts - sorry about that. Knowing both these amps, it does not gel with me to consider the SA250 as just being a more powerful SA100. Secondly there is a significant difference between the SA250 Mk3 and the Mk4. I don't mean the Mk4 is significantly better, but it is significantly different.
The word is, by the way, that US buyers are holding out for a Mk4 version of the SA100 and sales have slowed, causing Plinius to consider releasing a MK4 version, even though they have no upgrades planned. Kinda illustrates the false conclusions people jump to about how a family of products is developed.
Another little story - A friend of mine had a SA250 Mk3 and used it with his Dynaudios and found it lacked life - auditioned the Mk4 and found it went in the wrong direction for him, and believe it or not went back to using a McCormack DNA 1.0, because it gave the added edge that the Dynaudios needed. I relay this just to put the relative sound in perspective. I reckon his problem was his other gear which was Meridian 500 and 566-20, with a Sonic Frontiers preamp, and his insistance on using very ordinary cables.
Last point - if I had an SA100 and Dynaudios, I would be craving for more power too. The Dynaudios require a powerhouse amp and the SA250 may do the job, but may also be a little laid-back in this combination. The SA 250 Mk4 and Thiel 3.6 work really well together for me, but the Dynaudio is not the same kind of speaker as the Thiel 3.6, if you know what I mean.