Amp or speaker first, upgrade
I would do speakers first, as your Krell even though it’s a smaller one it still has good current, being Bi-Polar(BJT) output stage, and will drive most speakers out there and it’s not a bad amp, very good in fact.
If you do amp first and it’s not as ballsy (current) as the Krell then it may not drive future speaker.
Cheers George