What I liked about JEM was, the experience they have in RB's, the workmanship, and the service. JEM talked me through the whole process and didn't hide any of the possible costs that are going to be associated with work. In my opinion, a good tuner is someone who has worked on enough of the engines your tuning and should be able to foresee most of the potential problems and advise you prior (Not start the work and then say "oh this is going so I need more $$$ because you don't have this or this broke"). Now I understand that things happen and no one can predict the future, however, there are parts that a good tuner will know won't cope with the extra load if they have been regularly working on your type of engine.
JEM outlined everything right from the getgo and tested what they could before beginning the work, like completing a compression and leak down test to make sure that the engine was in good health before dumping a tonne of boost into it. The quote them at the time "we don't want you putting a whole heap of cash into an engine and tuning unless you know it's going to cope"
I also appreciated that when I picked up the car, Adam took me for a drive to make sure that I was happy with it and to answer any questions I had on it and the tune. I'd never had that type of service from previous tuners, usually its once the job was done, pay your bill and get your car out of their car park.
Would I go the -9's? Probably yes, although I'm one of those weirdo's that likes the lag, especially when it comes on to an unsuspecting passenger. lol
If you want responsiveness, then yes -5's, but as I'm sure you've read the best responsiveness you're going to get is from a single. There is a stack of benefits that come with running a single and its not just the power and its delivery, they're typically cheaper (because you're only buying one), less heat in the engine bay (always a good thing), fewer parts to break, the latest tech in single turbos make them animals.