Broke a few speed limits getting home to try the 4ohm tap - a huge difference and a big relief. The midrange in particular is much improved. Many thanks for the advice Rrog. However I have to go along with your comments Programmergeek; the speakers are still not as "bright" as I was hoping and as bright as I heard them in the demo lab (sounded great). Something still not quite right but a whole lot better now I have swapped to 4 ohm.
Cheers guys
Cheers guys