I had an HKS SQV on my Evo 5 and it worked well on it.
Nice noise too!
But the general concensus of opinion seems to be don't bother for a Skyline, hence I haven't fitted one to mine.
But, if it's what you want, then go for it. As I say, the HKS one is good. Haven't used or seen the Blitz one....
Andy T.