The no-fee Chase Freedom card is offering 5x Ultimate Rewards points at Restaurants throughout April, May and June so that’s a better rate than the CSP. The Ultimate Rewards points earned with the Freedom card can be combined with those of the Sapphire Preferred so that you’ll have a single pool of points.
If you don’t have a Freedom card but do have a Sapphire Preferred, why not sign up for one now? There’s no annual fee and even though the sign-up bonus isn’t great (10K points after spending $500 in 3 months) you can also get a 2500-point bonus for adding an authorized user and then you’ll have access to the quarterly rotating bonus categories.
Note: I do not have any affiliation with Chase and do not receive any compensation for any credit cards opened via these links. It will benefit another deserving blogger, however.