Well if you are going to consider the Mediastation and Wersi, for the type of music you are going to do (and for any type of music really), those keyboards could be what you need.
Always taking in to account, with hip-hop and other type of urban music it is not the sound source that matters as much as how creative you are with the sound.

Not that the Roland and Korg are bad but because of their closed OS their sounds and styles are limited. With the Wersi and Mediastation, you would be able to use giga samples and other high-quality samples on the keyboard with a generous sample memory.

The only thing is that there are not that many reviews on them so unless you are like some persons, and going to buy it like how some persons are buying the Tyros II, you would be best served to try and get some time playing with them taking a look at the OS and the key feel.