Have you run your car with the airbox removed at all? From posts I have seen before, it sounds as though you run your car as an everyday family car. With trumpets, the noise level will go up quite a lot. This is fine when you are in the mood, but could get wearing on long journeys. Of course, it would stop much conversation with your missus when driving - this may (or may not) be a good thing!
From my experience, trumpets don't do much to a standard engine (except make it noisier). When I have done tests on a rolling road, the losses at various points in the rev range outweighed any gains elsewhere. The car sometimes 'felt more powerful' on the road but wasn't borne out when measured.
How about a K+N panel filter in the standard box to start with and then getting the cylinder heads gas flowed, rally cams etc later?