If you’re using gold charge card or platinum travel card, go for Amex rewards multiplier to buy some gift cards. Gold charge rewards become 5x and platinum travel 3x respectively. No multiplier for MRCC I think, just FYI.
So earn more on your spends as well as monthly milestone benefit. Only issue is, if you can’t use your voucher you will probably end up selling at a small discount on trading section.
MRCC has 2X multiplier.