I've had the Special 25's for 18 months now and they've driven me crazy with their forward presentation in my room. They've cost me a lot of money on power cords, interconnects, 3 pairs of stands, new CD player, new amp (now Bel Canto eVo2i). You see, I bought them without hearing them. I had auditioned the 52SE and S1.4 at the local dealer and loved them, so when I saw a pair of Special 25's on here for the same price as the S1.4's I jumped on them.
The Special 25's I think are the odd one out in the Dynaudio range with their forward balance. I ended up getting 2 pairs of Contour SR's to use one as a centre and the other pair as rears, but I tried them out as mains and thought my God, there's that smooth midrange that I was after.
I have now just got in the S5.4's (from here actually, and disappointed in their physical condition, but I won't go there just yet)and they have the same more laid back relaxed balance of the little SR's.
In my room, the 5.4's walk all over the Special 25's. The bass is excellent, the midrange smooth and the treble so much more detailed and airy. I can't believe its the same tweeter.
I've never personally heard the C1's, but I strongly suspect from people I've spoken to, that they are the one to get. I only spoke to someone on the weekend who trialed the C4's at home, and he felt the C1's were the nicer speaker. He just couldn't get the C4's to sound right.
So yes, I'd go C1's.
I should have done this post after I sold the Special 25's, not before. God I'm stupid. No, go the 25's, I have a pair here, excellent condition.