Hi All,
Having started this post I thought I'd better give you an update.
I ended up fitting some Roadhouse '65 Specials to my Dragstar 650 custom. The sound is fantastic but it seems very loud. However, reading on this forum, I get the impression that is just because I'm not used to it yet. I have to wear earplugs at the moment. There are baffles and you can get quieter cores - which I'm looking into. However, the sound is fantastic - a really deep rumble.