No problem. The Sidesho battery should also fit your chargers yes. And yes your Blu battery should fit its carts and atty. I don't have a Blu, but from what I have read, yes you should get better everything. The 902 MV sells is thicker but its atty and cars should also fit your thinner Blu battery. With that, you'll probably get even more vapor. Depending on your budget you could get a Sidesho atty and carts, and a 902 atty and carts. Once you know what you like best, then get a matching set if you like.
To confirm all this, email Tony at MV and he'll answer it all. He's great!! But at least this way, you can spend a minimal amount of money to find out what works for you first.
I was sooooo unsure of filling my own carts and buying and cutting blue foam, but I decided to do it on the second day I think, and it was very easy even though I was so intimidated.
Tell Tony Billy Gardner sent you if you want but either way he'll help you before you even purchase.
Tony Kaeo
info@modernvapor.com
or call him which is even better at 877-312-ECIG (3244)