Cary SLI-80 Signature: 6550/KT88 shootout

Hello people!

Recently acquired Amp has me searching for some nice tubes.

Currently have Electro-Harmonix 6550EH, Svetlana 6550.

I don't want to sacrifice bass quantity or quality, but am interested in tubes that sound good without losing anything compared to these tubes, which are fairly cheap.

Any thoughts?