I say you should
The Attila of the Huns - Equilivent of Assyria but worse, they start with Horseback riding and their Battering Rams are DEADLY
Bouddica of the Celts - Quick Religion founders as they have a bias for Forests and gani +1 to +2 when cities are settled adjacent to Forests.
Dido of the Carthage - Starts with Harbors so Coastal cities gain Trade Routes (with Wheel) allowing you to have more gold, they are able to move over mountains if a Great General is earned (either way)
You already get Ethiophia with BNW
Maria Theresa of Austria - Can "marry" City-States and absorb them into her empire, gets a bonus to Great People generation. Artistically my favourite civ, but that's just artistically.
Pacal of the Mayans - Another Religious, not onyl that, they get to pick a great person every few turns as with Theology they unlock the "Mayan Calendar". You can only pick a Great Person once.
Theodora of Byzantium - Another artistically beautiful civ. They get a bonus Belief when founding a religion (but that's kind of obselete at higher difficulties), they do have the Fire-breathign Dromons though.
William of Orange of the Dutch - They keep half the happiness earned from Luxury Resources which means you can trade your last copy of a luxury resource and still get happiness from them. They also get the awesome Polders that can be built on Marsh and Flood Plains
You also get Isabella but you already have that.
Gustavus Adoplhus of Sweden - Amazing Diplomatic rival. Not onyl do you get a bonus to great people production if you have a DoF (which works BOTH ways and Gustav GETS MORE with multiple DoFs), but you can actually USE those extra people (like admiral and generals) to gain +90 influence with a city state.
So yeah, plenty of good civs
Not only that
The Into The Renassiance Scenario is very good, it's long and fun to play
The Smoky Skies Scenario is also a nice sci-fi scenario to play is completely unique experience
And then you have the Fall of Rome where there's a nice twist if you playwith the Romans.
So in short.. I'd say its' worth it. G&K civs were the first to be in my opinion truly unique. It was just a bonus such as twice this, cheaper that. They truly had unique abilities.