Ya know, that’s a good question, but somewhere I recall hearing that the current version of FCP is not as persnickity as it used to be regarding sample rates.
I didn’t see anyone here mention Episode Pro as an option. Formally known as Compression Master till it was bought by Telestream, it is not only a great encoder for DVDs but does a bazillion other formats as well. It cost about 800. BTW it does incredible standards conversion to PAL or NTSC direct to m2V in one step. Fantastic tool and great support from the Telestream folks.