Hey Phil iam having somewhat the same problem as you, i bought a little dot mkIII for my D2000.
And later found out that the little dot can go to 32ohm, i looked on the little dot forum and read that the MKIII powers the 25 ohms no problem.
David told people there that its best that you order the MKI if you only have low impedance ones, the MKIII would do fine on low and high impedance ones.
I would search on the little dot forum if i where you, you can find like 5 posts on the same problem.
I read allot of people experiencing problems with the mark IV and the Denons, something with background noise.
So i wouldnt go for that one.
I can tell you if the mkIII works as soon as it gets here, but that might be a while (week or so).
Edited by Deurklink - 8/24/11 at 2:43pm