So, I'm not in a WRX, but I have done a little research and I think I can use the factory WRX injectors as an "upgrade" in my car. From what I understand so far, the stock Gen1 WRX units are high impedance, and either 410 or 440cc (I was confused reading a few diff. answers), at 3 bar (43.5 psi).
The plugs are different, but I have no problem splicing the wires, and I also see companies selling pigtails to convert from the stock Subaru injector plug to the Bosch EV1 square plug, which is what my car uses.
My question is: do the typical Bosch-style injectors (TOP FEED!) fit in the fuel rail of the WRX?
Only advice I can give is that the WRX injectors look more like the first link you posted. The second link looks more like the side feeds that the 04-06 STI came with. The WRX uses Denso injectors, but I know for a fact that you can run Bosch EV14's since those are very popular for the WRX from brands like Injector Dynamics and Five-0.
You got it right on the specs though, high impedence and about 400-440cc's at 43.5psi.