AFAIK, the T and P Series (and W, if you go used) ThinkPads have a fantastic reputation. They're business-oriented, though, so you'd likely have to go with some super high-end model to get a good GPU. At that point they're either pretty expensive or pretty old. I got a used W540 last year over something new because for the specs I cared about (HiDPI screen, lots of RAM and internal storage bays) it was something like 1/5 the cost of a new machine. Of course, a new machine would've had a way better CPU & GPU, but "1/5 the cost" is pretty compelling when you just want something to explore Linux with. I don't know about specifically the ThinkPads with a Risen 4000u, but as I understand it, in general the 4000u is kinda the king of the "normal" laptop CPUs right now, as long as you get one with dual channel memory.