Welcome to the dark side...
Grendel like all calibers you can go cheap or high dollar. The good thing is the "cheap" stuff is not always bad and Grendel is getting much more popular. I went with a Brownells 18" barrel and love it. $300ish WITH matched bolt. 123G amax it shoots sub MOD all day long. Other guys will spend $600 on just barrel. The nice thing about grendel is that other than magazines, bolt and barrel it uses all stock AR15 parts. SO honestly, if you already have an AR, just build an upper. I put a Primary arms 4-14 FFP scope on it and the pairing works very very well. Everything else is generic low budget AR parts. ALG Defense Combat trigger and Troy Alpha rail are only upgraded items.
Check out
www.65grendel.com for tons of info.
The great thing about Grendel is you have a big game capable round (6.5 been taking large game for centuries, just be smart about distance/velocities for terminal bullet performance), with fantastic ballistics (drop similar to a 308) and very low recoil so pretty much anyone can shoot it all day long with no fatigue.