symphonic Line RG4 III vs RG4 IV?

I only got a quick glimpse of the "newest" version vs. the previous one (I assume the "newest version" was the MK IV). These latest amps were probably NOT fully broken in...

As Symphonic Line products have a long life-cycle, but this IS a "new" version, there MUST be differences... Well, they didn't sound so earth-shattering to me.

The quick subjective results were:
*the new sound was slightly more extended in the upper highs & less full bodied..
*the typical S-Line sound was there (i.e. dynamics, transient attack, sense of "speed" etc) but the old sounded a tad "slower" and a tad more refined: as "speed" is a nonsense per se, maybe a matter of higher biasing towards class A in the newer version?
*overall, between the two, I wouldn't be hard-pressed to exchange one version for the other: if I had the earlier version, I'd stay with it -- OTOH if I were on the market for a pair of amps, I'd go for the current version...

The pre was an RG3+ turbo PS & speakers were Triangle Magellan. Again, this was just a quick listening session at a dealer's, no measurements taken, equip probably not broken in, etc.
Cheers

I haven't heard the latest Mk IV amps but when I got the Mk III version (That I still have), I was told by a long-time Symphonic Line dealer that the midrange on the Mk II version was better than on the Mk III 'cuz the Toshiba output transistors in Mk II were better than the Sanken transistors in the Mk III.
Looks like something similar has happened bwtn Mk III & Mk IV.
Seems like one gets the extension at the cost of richness. There is a person here who claims that he can modify my RG4 Mk III to have even better sound. Maybe I will take him up on his offer. The modified sound might approach the Mk IV sound???

dear Gregm,

I saw the RG4 IV, but not sound or music from it.
from your comparsion, maybe I will prefer the MKIII sound. A local dealer told me, SL is changing its sound due to change of designer? is this true? thanks

Tim