A:Answer I would suggest to check out a Dell XPS 15 instead, if you like the idea of this laptop. You can get good deals on refurbs. The main issue with the UX501VW is that it uses a PenTile (RG/BW) not-true-4K display. You risk app scaling issues without actually getting the full sharpness of 4K in exchange for it. A consensus on laptop forums is that this is deceptive marketing. The 4K display in the XPS 15 is the real deal, and the FHD models are fantastic too. The sidebar on http://reddit.com/r/SuggestALaptop/ has more info on this whole issue.
Also check the software you plan to use to see if it scales properly on high-DPI screens, before you get a '4K' laptop, true 4K or not. Ableton, in particular, seems to work with a few tweaks, though third party plugins may appear tiny still. https://www.reddit.com/r/ableton/comments/3uophe/proper_scaling_on_4k_screen_fix/
FL Studio I'm not sure.