Anything powered will do. Get an A-brand if you can. There has been a review on USB-hubs on the main site you might want to check out. Not the most up to date perhaps, but then again, nothing much has happened on the USB front anyway.
Don’t get the cheap stuff, spending a few bucks more will pay in the long run.
Personally I don’t think there is any need for 3.0 hubs. Your chances of NOT having any compatibility issues are way better with a 2.0 hub. Also the bandwidth with 2.0 should be plenty for a bit of Midi traffic and your sound card.
The only reason to use USB 3.0 (generally speaking) is if you want fast data transfer (USB sticks, external hard disks and such)
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