I have the 150w sigelei, Its fantastic!! I did the cheap mod then variable then mech mods then to the 150w
I wish I had just gone straight in and got one! cant go wrong with it. You will never be wishing you had more power but its there if you need it
Subtank is a great way to get into sub ohm and trying to rebuild on the spare base
If you don't mind the inital outlay then 100% go for it. If you want to save a few quid you could get the sigelei 100w Plus. But the 150w looks better
The sigelei mini 50w would also be fine with the subtank which is even cheaper still
You will need to buy some high quality batteries for any box you buy, efest purples, Sony vtc or Lg. And a decent battery charger or you will destroy the electronics in the box