There are some expensive name brand juices out there... and you'll never know if it's created in a quality clean environment. DIY is what I do for 99% of my juices now. There is a huge DIY section in this forum. There are recipes for hundreds of clones of the name brand juices. If you vape a lot (especially in deep sub ohm - .3 or less) it's the cheapest way to go. It's something you can read up on while you learn to vape the new gear.
This thread usually has sales posted on many juice lines :
DEALS and STEALS -
Deals and Steals (go to last couple pages)
There are also a dozen sites where you can get 120 ml of juice for $20.
You may find that the 6 mg juice could be a little strong in the new gear. The issue is the Subtank Mini with your kit will vaporize more juice than the little coils of your Aspires. With the 1.5 ohm coils it may be a slight difference not to worry about, but if it is an issue you can always buy the same flavor juice in a zero nic and combine the two to cut the nic in half. 2 parts zero nic juice and 1 part nic juice cuts the nic to 1/3. Simple math and an easy issue to solve.
(We're probably back in the info overload) Don't worry, just relax. You can find the simple answers to what you don't understand here.