I think they're about 180kw/300nm. I've not personally driven one, but have heard good things about how smooth the power delivery is. The turbo obviously offers easier modification and more torque, but the H6 has no turbo lag. I stick to 4cyl because the rego and economy is a little better, but would have probably gone the H6 Gen4 had money been more of a factor for me when I bought the WRX to update my tiring Gen3 B4.
If you can find a tidy 2.5T GT then that would be my pick though, 4cyl turbo Subaru's are fantastic. I was just suggesting it as an alternate option before considering a Gen5.