You can use custom roms.They are smooth .For example PMP Ultra I use this rom. Because, it is smoother than stock rom. And there is no supported C11 from for SGS duos.They have network signal problems.
I am new to the rooting world. I have just rooted my S Duos and installed PMP Ultra ROM V8.1. The performance is not as expected. I still notice a big lag most of the times. Have I done something wrong. Should I try KyleOpen. Please give your valuable suggestions.