It is very easy to edit sounds on the X1/X4.  Just push the edit voice function key and you're there!  At this point you can change filter, envelope, LFO, etc. and then hit save/enter and you can save your sound.  The 8000 and 9000 keyboards are the same action, and as Fran said the X1 is semi-weighted.  The keys look just like any other 61 note synth keyboard, but if you feel under the key you will feel a glued in weight.  This is what makes it semi weighted.  The selling price for a X4 will vary because there will be 4 different models offered.  If you want prices you will have to contact one of us dealers directly.  I don't quote discount prices on this forum.  This forum is primarily to discuss topics and ask questions about keyboards and the way they work.
George Kaye
Kaye's Music Scene
Reseda, California
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George Kaye
Kaye's Music Scene (Closed after 51 years)
West Hills, California
(Retired 2021)