I have Remus Gran Prix cans on my '03 DL1000. I love them. They have a nice mellow sound and it doesn't intrude on me at hiway speeds or when riding for hours. They will bark authoritatively if you blip the throttle. I bought them through the US distributor in California - Max Moto. I had the bike dyno'd before and after adding the cans, and they did produce more horsepower and torque (in the vicinity of 10%). They do not ever require repacking. I did not modify the FI, and I see no need to. I highly recommend these.
I actually liked the Remus cans on my V-Strom so much that I also put a Remus can on my Burgman 650. That one was more of a project, because it was a different model that came with a removeable baffle. It was too quiet with the baffle in - louder than a straight pipe Harley with the baffle out. I ended up modifying the baffle myself to produce a nice sound level. But once I got that straightened out, I like that can too. Max Moto was easy to reach by phone, and helpful, while I was working on that installation. I was the first person in the USA to install the Remus can for the Burgman 650. They gave me a nice discount for being a "tester". I did have to provide email feedback and some pics - no big deal for a discount that was about $100 as I recall.
In both deals, the Max Moto price included shipping too.