I have not used Yamaha PSR740 nor PSR8000 and so am not able to answer your first question. About using X1 styles on PSR740 you cannot use X1 styles directly on PSR740 because they are stored in different format. To port X1 styles to PSR740 you have to either use an expensive software called EMC StyleWorks (http://www.internet-stadt.com/tastenshop/) to convert Solton styles to Yamaha styles first. Or you can buy a USB style CD for Yamaha, it is just released and should contain Roland, Korg, Technics, General Music, Yamaha and Solton styles {should be over 3000 styles) and costs about $120.