The ASUS AC-68U Router is a really good router and the refurbs are a good deal. The trick is turning the T-Mobile TC-1900 back into an AC-68U.
Thankfully, there is a great tutorial. The key is to follow every step, in order, and not skips.
You can turn a $50 router into a $130 … as long as a little geek doesn’t scare you.