Decisions Decisions Deciscions

Ive been looking at a Safety 1st stroller combo set (carseat and stroller) but idk if i should just get the carseat by itself. We have a 1 & 3 yr old boys. We also have a sit and stand stroller we use only to go to the zoo just in case 3 yr old wants to ride. Normally he walks.. Also have a $14 stroller from Walmart we keep in the trunk for the 1yr old. The sit and stand stroller is kinda big so it stays home. What does you ladies think? Get the combo set or just the carseat by itself