Lets not put a fork in it just yet.
$6,000 on SPG that you have anyway=$132 of rewards at 2.2cpp.
$6,000 on Blue Cash=$360-$75 annual fee for a card that was only really rewarding on groceries-$132 you could've earned on SPG for that spend=$153.
I don't think $153 is worth the hassle of another card to keep track of.