Main drivers:
174 Discraft esp nuke
175 Innova star valkyrie
175 Innova champion starfire
Fairway drivers:
175 Discraft pro d cyclone
175 Innova champion sidewinder
175 Innova champion eagle
Mid range/ putt and approach
174 Discraft pro d soft magnet
174 Innova star san marino roc
What should i add to my bag next?
How far are you driving realistically?
Your Sidewinder is actually a distance driver, so I'd agree with Vegan Ray and throw a Leopard in the bag. I carry two (a new 175g glow Champ, and a older 175g Champ) with me at all times, and I'll use them on low tunnel drives out to 300-325'. Leopards are extremely versatile since you can use them for turnover drives, straight shots, woods, etc. If you get one, I'd personally recommend a Champ version.
As Discspeed said, an understable mid would be a great addition also. I personally like Star Stingrays. I've tried Meteors also, but I like the Stingray just a little better. Plus, both discs can be great for longer, straight midrange distance shots if you add a little hyser to your release.
And as I'll always recommend, add a Teebird. It'll have less HST compared to your Eagle, but it is a laser-beam producing disc that will leave a smile on your face again and again after you learn to throw it.
If you've got room, leftover money, and the arm the throw one, an overstable driver such as a Z Pred, Champ/Star Firebird, or Champ Banshee would be great additions to the bag as well.