Yes, the ones in your pic are STi V5. Mike Shields does carry them.
And AV Sports is indeed in Arizona, and the seats you're talking about are European-market WRX seats, pictured here in my attachment. They were selling them for under $600/pair. Yes you read that correctly.
If I were you, I'd go with those. STi seats are nice, but pricey!!!
The only thing I hear is that those WRX seats sit a little HIGHer than stock. They're take-outs from the new bodystyle, which has a slightly different seating position, that translates to a somewhat higher seat when placed in the GC8. Kind of the opposite effect from what's needed really, in an Impreza. It's a very high-seated car.
However..... if you can find a pair of the OLDER Euro. WRX seats, from the GC8 bodystyle, that should be a better setup. I just can't find 'em anywhere. They were black and grey.