Is it my amp or my speakers?

Most definitely the speakers. 

I owned a Krell KAV-300i for a while.  It had a grainy edge that made it hard to listen to.  I think A Vincent SV-237 would give you more of what you're looking and you have the option of rolling tubes in the preamp section.  Simaudio makes some really nice integrateds, but they are going to be more neutral (are you sure you want "bright"?), but lots of detail and definition.

I had the Tekton M-Lore, and I thought they sort of smoothed everything over.  So, in my opinion, you'd be best served by finding different speakers.  Also keep in mind that speakers will have a much more significant impact on the overall sound of your system than an amp change.  The Krell should drive most speakers without issue, so I'd suggest reading up on speaker reviews and trying to demo (if possible) a speaker or two that seems like it has the sound profile you're looking for.  Places like Crutchfield and Music Direct have trial periods that will allow you to hear the speakers at home with your system.    

Good luck and have fun!
Scott   

ignoring your speakers for a minute, i see the other gear you have i would say the sound is bright, a little harsh in the treble, a little recessed in the mids, strong in the bass

so if you seek brightness, it has gotta be the speakers - i don’t know the tektons, much less your tektons... they make so many models covering the waterfront, no idea what is the sound character of yours... tekton’s better speakers certainly are known for their impact, neutrality and clarity - your specific model, maybe not... other poster below says they are smeared/smoothed over ... that may well be spot on...

Assuming all units of model X sound the same is not a safe assumption. Some may operate better than others. Especially older gear and even if work was done on it.
Not saying it’s the amp but not possible to rule that out with the limited facts on hand.
If not happy then try something different and see what happens. The Bel Canto c5i is an integrated that is never inherently bright and can drive most any speaker to modest volume well and would not cost much to try used.

But assuming the amp is working well I like that Krell very much and would hesitate to part with it if it has served me well over the years.

The Tekton Lore would be more special were you using a modest powered tube amp. With the Krell in good operating condition or with other similar quality beefier SS amps, you have unlimited speaker choices that will match up well.