Which Neu motor with 5S and Quark 125

What's it going in? Is that 5S lipo or 5S A123?

Personally, for a 5S setup, I think the 1515 2.5D is hard to beat. That will give you about the performance you'd get with the 2200kv motor on 4S, but will stress the system less because the current draw will be lower.

I try to stay away from high kv motors in trucks. I like the 30K rpm neighborhood. Again, assuming that this is going into a truck, you're only other options would be the 1Y (2200kv) or the 1.5Y (1500kv).

I don't own a Neu, yet; but I have been running lots of Feigao motors. I'm running an 8XL, which is pretty close to the Neu in terms of kv rating, and my Muggy is downright nuts on 5S. I was going to jump on the 2.5D, but after having seen the 8XL run on 5S, I'm thinking that I might go for the 1500kv motor to keep things sane. I might just order up a 9XL and see how I like that, before I drop the bucks on the Neu.