Hey neepheid!
Sorry I didn't read your reply until after I sent my post Doh! I think you have adequately answered my question!
The RedSub looks very much the same beast as on the link you provided regarding the Promethian
http://www.beta-aivin.com/English/Products/Bass/BT/English_205.html
So I strongly suspect that the RedSub is just a revamped model with a red speaker cone and basically exactly the same!
Regards
Lostfollicles