As you are running the car on a track I would go for the full synthetic. Preferably the 300v line, and 40-50 grade.
Whilst the sales blurb sounds good, the 4100 is still just a semi syth like many others. I don't think the 6100 is availabe anymore in Oz. You are better off with a full synth in a turbo.
The Motul oils are not really that expensive. I buy 4 litres of 300v for $72.00. The 8100 E-tech would be abt $80 for 5 ltrs, however I don't see the need for a 0w and I don't really like the 40 point spread.
My son has a highly modded Nissan 180sx running 1.3bar of boost and he runs it hard. He has run the 300v 10-40 and is currently runnning the 5w-30. The 5w-30 is a high 30w, almost a 40 grade. He changes every 4-5000k. He does have an oil cooler, which probably helps.
Subarus , from what I've seen here, like the 40-50 grade oils, but even if driven hard (I think most Wrx's are) are pretty easy on the oil. Check the UOA section, plenty of really good reports.