I can't comment on the Invida .. . but since I had a Miltek, combined with HFC's its close IMO to a Nismo (nothing will be exactly the same) Graham, Dave and Will also had Miltek and HFC's. Great sound, you will always get a small about or rasp with HFC's but the louder the exhaust the more accentuated the rasp will be.
If I was to go again with a 350 and Exhaust I think I would go with a Tanabe Medallion, slightly deeper note than the Miltek