The skys the limit. Off the shelf, STI from beginner to semi custom.
Then after that , Brazzos tuned STI up to Brazzos custom.
Then after that, full blown custom builds from mild to wild. Just like racing, how fast does your wallet allow you to go.
And now there are overseas companies getting in the game, SPS Pantera (sti clones)
Then there is all metal frame Para, or custom built Caspain frame guns.
And then there is the gently used guns, heavily used guns and then....
what in particular are you interested in?