So, Korg (Hartke suppliers) have contacted me back, and quickly too, £110 for 1 x 15" XL speaker posted or around £180 for two. Now the cab cost me £100, but i do like it...it has heavy duty castors , is well built and weigh's a ton which is great for my band as they love to carry it .
Interestingly Korg in my email put the speakers as 300W, not sure if that's a typo as the originals were 200W, but 300W would be preferable if the newer speakers are that.
But i can't stopping thinking about some decent Eminence speakers like the 3015LF ...but then there's tuning the cab, physics lessons etc...BTW how do you tune a cab? And how do you find the litres of a cab?