Remus are excellent. No 2 ways about it. In the UK, they now come with a lifetime warranty. Fantastic build quality, fit, and a very distinctive sound, esp at high rpm (4000+)
I had one on my Fiat Tipo 16v, and it was awesome, (although the car was de-catted as well.)
The only thing that comes close to Remus is Supersprint, but I prefered Remus for it's unique sound.
It can be best described as a 'rocket' sound, when driven at night, along a wall, or through a tunnel, with the windows open.
Hope this helps.