Looking to pick up some opamps for the minibox-e+ .... lateral choices at worst

looking to improve sound but I know that depends on taste. Just don't give me a likely downgrade to the overall sound

Would love some particularly high-end choices for this slot
According to the site for it at head-direct:
"OP-AMP requirement: Most DIP8 mono op-amp"
I'm a newb so I don't know what will work and what won't, so try to be sure before you sell me something I can't use
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