What's the best branding rod for around 80-100$?

"best " is subjective. I have had several cranking rods in that price range, and they are all good. The ones I have or have had, are the Veritas winch, the BPS cranking sticks, and the st croix mojo.

For that range, I would agree the St. Coix mojo would be an excellent choice. Unless you are throwing heavy deep divers.

6xd?

Fenwick HMG or HMX, Okuma EVX-A  Ethos H2O  Deisel  Crankin' Stick are a few in your price range.  Haven't used my Crankin' Stick enough to form an opinion.  I have 4 different Fenwick models (HMG, Smallmouth, River Runner, Aetos) and like them all.

St Croix Mojo Glass.  It's more around the $120-$130, but I wouldn't trade it for any other cranking rod in the same price range.

Academy Ethos cranking rods are $60 at full price, really like mine. There's a 7' 10" MH/M version just for big cranks like a 6XD too. 

6xd?

 Personally I'd go longer for the 6xd and similar cranks. I use a 7'11", but a 7'4" and up should do. It really helps for distance. Of course 1/3 of the retrieve is the getting down, 1/3 is strike zone. and the last 1/3 of the retrieve is the upward movement to the boat. The length also helps handle that harder 'pull' that those larger lures give you. Again, just my opinion- Im sure lots of guys throw a 6xd with shorter rods and have success.