I was just there last week. I remember seeing a Guitar Center, but I can't remember seeing anything else. And I saw where Vai is going to play, right downtown.
I DID manage to go to the Experience Music Project museum while I was there. The guitar room has an original 1952
Les Paul with a trapeze tailpiece and a Fender Broadcaster, among others. No Ibanez, though. It's a nice little museum, but don't expect too much out of it. It's directly below the Space Needle, so you can't miss it.