The PSR 9000 USB Interface Card is available from Musitronics. You can find the page at the following URL: http://www.musitronics.de/indexe.html
The Price after shipping to the US is around $143.00 US.
I did the installation myself. However, they recommend that you take it to a authorized service center for installation.
Prior to your purchase of the product, you can download a PDF file that shows the installation guide. I noticed a few things that didn't seem to be covered by the manual. One nice thing, they have started including the piece of metal that fills the small knock out that you remove to install the USB connector in the rear panel of the 9000. All in all, I think anyone with a good degree of electrical and computer experience should find this to be a simple self install. The gentleman selling the product is very nice and quite helpful. It did take a couple of weeks to receive the product, as it comes from Germany somewhere. I think that covers the basics of this great product. If you have further questions regarding it or how well it works, feel free to contact me.

Regards,

Dennis