Warm Tube Amp(s) to Tame Hyper-Accurate Speakers?

I second other poster’s comment on cables, without knowing what cables you are using, power, interconnect and speaker, no one can tell you why things are off. Another high probability is speaker placement in the room and toe in, it’s very likely you have placed the speakers in the right spot for the bass to couple to your room, therefore tonal balance is off

Even Spendor D9.2 drivers would benefit from grounding wires. Don't believe me? That's okay, but do try it and I'm sure you'll be bewildered and amazed. Those troublesome sources that sound harsh will suddenly be fine.

If a Conrad Johnson amp can't fix it then you should ditch the speakers. Having said that way back I had a pair of Spendor BC1s and still rate them highly. Maybe things have changed at Spendor.

+1 @hilde45 on room acoustics. Often neglected but it is what will make it or break it. Good luck. 

These speakers appear to be absent a bi-amping option. With that, one is arguably  at the mercy of the speakers voicing and minus a remedy to work around any perceived short comings. Ouch