I'll tell you what I went for as you know the gains I have.
Cosworth panel filter
3" decat downpipe
3" cat back back resonated centre exhaust
Roger Clarke Motorsport fuel pump
Ecutek remap @racedynamix
3 port boost solenoid.
My full exhaust cost me £100 I don't know the make as it was second hand but made really good power so I can't complain.
As to filters. Some like panel some like cones. Jury is out. I went for a panel so I could keep the standard looking engine bay.