Just going to jump in since others have already mentioned myvaporstore and you asked about them. Vapoor eyes was a God send to me when I first started out Vaping back in March...he's the one that recommended MVS and the Vision Spinner batts...sooo glad I listened to him! I now have 3 Vision Spinners..along with a couple Vamo's..anyhow..that one site you listed with a kit..the one that was NOT MVS...it was a small Battery that came with that kit. Meaning you won't get just a whole lot of run time before you're gonna have to charge it up. Me personally, the 1300 mAh that the Spinners have are great! Can go all day long without having to recharge. I didn't care that it was a bit bigger..if it meant longer time in between chargers, better for me.
Like you, I like having quite a few tanks going with different flavors...and hated having to switch out tanks on batteries. Since you are the same way, then yea, I'd go with 2 more VV. Like I said, I have 3 of the 1300 Spinners..been using them since March and have NEVER had a problem with them.
I have order quite a few times from MVS..and almost every time, my order shipped within 24 hours. They have a 5 or 10 % coupon code around here some where. You'll really like a VV battery though. Like others have said...some juices taste better at a higher Voltage...but then others taste better at a lower one. I bet if you get the VV battery, you'll rarely ever use just a regular battery again..unless its just because your others are dead.
Just wanted to throw out the whole mAh on the batteries though...if you are wanting to go longer in between charges, then don't get a smaller battery...because that one kit you listed, was for a 650 mAh, I believe it was...that's only going to give you roughly 6 hour Vape time...depending on how hard you hitting and what not..a 1300 mAh Spinner while give you close to 13 hour vape time. You probably already knew this..but just wanted to throw it out there in case.
Good luck!