Thanks for joining the AndroidPIT forum!
Why are you thinking of getting a new phone? Are you not happy with the Galaxy S4?
If you are looking for a brand-new user experience, you might want to consider a Nexus 5, which has the stock Android user interface, much different and less invasive than the TouchWiz UI on the Galaxy S4. The other Samsung devices are really similar in many ways to the S4, so getting an S5 for example, has its perks, like the dual downloader, fingerprint scanner, super power saving mode, some nice new features, a cool camera with real-time HDR mode....
If you want something good, but that won't put a major dent in your wallet, you should consider the Motorola Moto G, which has a lot of people are AndroidPIT convinced!
Have a nice day!