I have a Galaxy S2 (T-Mobile) running 4.0.4 and I've never wanted to upgrade because I just need to call for the most part. I think the gps on it could use some help though. Anyway, I have 2 other phones Galaxy S4's on AT&T and they're running 4.3 I can't just select "software update" on the S2 like I can on the others because I get the "no firmware" message. Even though I've never done an upgrade, I think I have to do it via USB and Kies. Is that correct? Should I upgrade? Thanks for the help!