If you are buying the X1 HD, you will not need any more styles. You will already have 198 factory styles at your disposal, and not to mention 400 odd styles on the HD in addition. Some of the 400 styles are from their commercial disks that Solton sell, and the rest are from previous solton keyboards such as MS100, MS60 etc...
Put it this way, you will not need to buy any other styles. And as its already been suggested, we kind people will provide you with any more styles should you need them!!!
Ketron SD60, Ketron SD7, Korg Pa1000, Yamaha SX900, Yamaha Tyros4