Thank you Uncle Dave for replying.A sub woofer might certainly be worth a try and maybe mix it with some smaller speakers for higher octaves.
Maybe I am hard to please but I have yet to hear a keyboard amp that sounds good at loud volume.Most of them seems to either be very sharp with keyboard top notes or if you decrease the treble,the lower notes begin to sound like a bass guitar,especially with piano sounds and as I play live with a drummer and bass guitar,things start to get muddy.
I will have a go at your suggestion. Cheers