I would combo them with a less restrictive aftermarket exhaust, this depends on your budget. HFC's are a less restrictive catalytic converter, will allow passing of an MOT. The Garage in Motherwell where mine were fitted, offered an indepth explanation on the differences. The HFC's are from the manifold to either your Y pipe or straight through exhaust, to backbox.
You will get a perfectly grown up sound with most combo's, as a 370 should sound, if you can stretch the budget, then IMO, the Akro is the best on offer, there are loads on here running different combo's though, Stillen, HKS, Scorpion etc.
The HFC's alone will not give you your desired effect.