Is it my amp or my speakers?

I've been dissatisfied with my system of late--wanting a little more brightness and color--and can't decide if it's the amp or the speakers, or both. Here's the set-up:

• Krell KAV-300i integrated
  
• Cyrus CD-T
• Schiit Gungnir DAC
• Tekton Lore speakers

The Krell was a hand-me-down (!); everything else was purchased new. The amp had some overpriced work done to it a few years back and I'm wondering if the workmanship is starting to show, or possibly its age (~25 years, I'm guessing). Or, are the amp and speakers mismatched?I can afford to invest about $3K in the system, but am unsure where best to put it.Any thoughts/advice would be much appreciated.