I did the 2.25" Fullsac cores on my '08 SERK with TTS. It ran well for 45000 miles when I sold her to buy the 15 SESG. I installed the 2" FS cores and screens on this SG for better performance and a slightly more tame sound on the slab. I also installed the Fullsac DX headers and TTS MT2 with Steve's tune for this build. She is now the best running Harley I've had in 25 years. I was blown away by how tight Steve's tune is. I don't think I will even bother to do any tuning runs myself.
IMHO the 2" core has the perfect blend of performance, sound, and price. As others have said, why replace the beautiful stock cans when all you really want is to replace the baffle with something that will let her breathe. Once you realize that, you may as well use the headers from the same company. Yes, Fullsac still provides a discount for forum members so make sure you ask. My entire kit cost about $1,100: DX header, 2" cores, screens, and MasterTune2 with cables.
If you're like me you'll do the work yourself. I enjoy the wrench therapy, know it's done right, wand there are no unexplained scratches that always seem to appear when I let a dealership touch my bike. There are some great videos on the web if you google it.
Good luck! Let us know what you choose.