Asking about DF item exchange

I've suddenly come to want two items from the DF now. My understanding is that DF items are +1, past items are +1 → S2, and current items would balance out at S3? Is that correct? Would it be faster to look for them on the Marche rather than trading? I wish I had bought them back then, but they didn't appeal to me at the time, and now they do…. (Note: I've only spent 160 yen and on tours, and currently have 67,000 Happy Points) Planning to save Happy Points as much as possible until the next Marche. I've never drawn from the lucky bag before.