Is this a solid build?

Two points. First, there are better PSU's than the CX series from Corsair
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

Since you don't need a 750W, a 650W model is sufficient. Here are four suggestions, I like the Seasonic SSR-650RM.
https://pcpartpicker.com/product/kz7CmG/evga-power-supply-210gq0650

Second, I have concerns that the 1500X will bottleneck the GTX 1080 Ti. It is a little difficult to say for sure but this document shows the i5-7500 (equivalent performance) starting to bottleneck a GTX 1080.
https://docs.google.com/spreadsheets/d/17VRKPjyiTBx9Ewc2xkmaMZD2tA3gSOG3rNtH4OEiz3g/edit#gid=0
http://cpu.userbenchmark.com/Compare/AMD-Ryzen-5-1500X-vs-Intel-Core-i5-7500/3921vs3648

Not sure if this is an issue.
 
I didn't pick the 1080ti, a friend thought he could just pop it into his current build with no problems. Its a VR build and I went with 750 because it was the same price as the 650w I found at the time.

 

Went with AMD/Ryzen because a bunch of people on other forums told me it was better and Intel/i5 was over budget. It's for VR, csgo, overwatch and as a workstation.