I use Brodex 650ltr DI system, robust, very well made - basic and simple, not over complicated.
I agree with comments about aftercare, but to be honest i have found that they have sorted this problem with me, obviously i cannot comment for others.
I just want something that does the job, basic, well made, simple and doesnt cost the earth,
I have had Ionics years ago but found the system very good, but too much mither with it being all singing and dancing
My vote goes to Brodex, and if you need a chat i am only too happy to help