Hi Frogfish, I may be able to help a little. I own 205/2s driven by a Class A Musical Fidelity AMS 35i and they sound stunning.
The thing about these speakers, is they will get better and better as as the quality of the amp improves. They are fairly efficient, but have an impedance that drops to 3.2 Ohms. This means that the amp must have big reserves of current....preferably doubling its power into 4 Ohms and even into 2 Ohms (if you're lucky).
What amp and source did you hear them with...and what source do you have at home?
Your question about whether the Sugden will drive them properly (do them justice) is a difficult one to answer, as it depends on your definition of "properly".....it also depends on what you're comparing it to.
What I will tell you, is that I haven't come across a 30-40W Class AB amp that would do them justice...but IMO. Class A is a different matter. What I can tell you, is that my 35W amp drives them better than any amp I've tried, up to a 300W Coda CSi. It won't of course go as loud (but loud enough in a large room with a high ceiling), but the transient response, bass punch, detail and realism, is better than anything I've heard under £10k.
I haven't heard them on the end of the IA-4 so please take my following comments in the light of this. I think the Sugden will drive them reasonably well, but it's certainly at the bottom end of what they should be powered with.
The IA-4 has 33W into 8 Ohms and 45W into 4 Ohms. Compare that to the AMS 35i which has 35W into 8 Ohms, 70W into 4 Ohms and nearly 140W into 2 Ohms. Don't get me wrong, the Sugden is a fantastic amp, which I would own if I hadn't thought the MF was worth the extra.
FWIW I think you should try it out and see what you think, and I think it will sound good....but further down the road, to do these speakers justice, you will need to look further up the Masterclass ladder, which is an expensive business (LA-4 Pre + MPA-4 Monos!!).
If there is anything else I can help with.....ask away.