I got a Shoei Multitech with a Scala Rider clipped on, it works great for me. The helmet is top quality, not cheap but worth the money. Scala rider is the old type, 4 yrs old and still going strong.
I know you can get helmets with bluetooth built in for between £100 and £150 but the quality shows. Depends really what sort of use your going to put it to. For long times in the saddle I'd recommend the best quality you can afford. I haven't tried a Schuberth C3 so can't comment on that although some seem to like them, hell of a price though.