Wotcha and welcome.
Wrt to selling I was in a similar situation to yourself so struck a deal with a local trader and he got a fixed fee for the sale, I got hassle free sale
As you said high mileage is no issue if looked after but buying second hand will always be a gamble where ever it comes from.
XT's are desirable motors so good ones dont hang about and be prepared to travel for the right motor.
Later models have a 2.5l engine as opposed to a 2.0l this gives slightly more power and low down torque.
There have been issues with ringland failure on some 2.5l lumps - I dodnt have an issue and many others havent but oil starvation & detonation have been blamed for the failures.
It comes down to the material subaru used in its pistons.
Manual vs Auto - yes the manual is slightly faster 0-60, it is the same with my impreza, the auto will have a manual esq mode which enables you to change between the four gears. Which should you choose, entirely down to driving style - if you like stirring the gearbox an auto is not going to give what you want even with the semi auto option selected.
Keep us posted as to your progress