Zd542,
The amp is still breaking in, the dealer said that it will take closer to three months rather than the 400 hours Simaudio states.
The Audio Research DSi200 is not one of their tube amps, it's a SS preamp and a Class D amp. You're right, the upper frequencies are a lot more revealing and natural now. But I don't notice them being overly bright. That's why I don't think that's the problem, although repositioning the toe-in of the speakers sounds logical with the change.
Thanks,
Chuck