It is mostly about personal preference, to be honest, and the Lunhui is not tournament illegal.
I'd suggest an AV, Guhong, or even a Ghosthand, and wouldn't actually suggest a Zhanchi quite yet, to be honest (that's some extreme overexposure you're going for there). Looks like it's a bit late, though. An AV or Ghosthand, or Guhong are probably some of the best starter cubes you can get, in my honest opinion. If the best cube you've solved with a Rubik's brand, then I think you should probably pick up one of those three.
P.S. I can generally get 25- seconds on a Rubik's storebought.
Edit: As for my question:
It's a bit of an odd one, but where can I get the BIGGEST 3x3x3 cube that's mass-produced, or at least at a reasonable price?