Originally Posted by sohlman
From a UK perspective there is lots of choice for 4" Speakers. They can easily be made to fit with adapters. However for the 8" Underseats there is basically no choice. Earthquakes are very expensive and Jehurts and MB Quart's can only be bought as a complete set. The subs / mid basses can't be bought separately. Thus in my opinion you would have a far great market if you concentrated on this option.
And there is Gladen one kit as well. (tweeters / mids / under seats) and they are 100W and very affordable.
James, If you have not bought MB Quarts, I would suggest you to consider Gladen one kit.