The downpipe on the mkv gti/ed30 is not as restrictive as the previous mk4's were, but the rear section seems not to be as helpful.
so keeping the downpipe and changing the rear could be an option.
A full system is always going to be better though Keith. I will be interested to see and hear the Remus if you get it fitted, but I still think you will still be strangling the car with the stock downpipe and an aftermarket cat back. Dont let Jims words of wisdom wear you down lol.
What you should try and do is get Owens car and your car on the same r/r on the same day to compare, as you have almost the same spec bar the exhaust.