Not an easy question and one we'll all face in some way if we do track days. I think you've got 3 options if you can't afford to write the Subaru off:
1 - look at different insurance to get better cover
2 - sell the Subaru and buy a dedicated track car
3 - buy a track day hack and drive it to events or tow it behind the Subaru
For the cost of a set of new discs for the Subaru you could have a track day hack...
I'm tempted to suggest buying a car you can use for track days and for racing, but racing is many time more expensive than doing track days
Let us know what you decide!
Nick Froome
www.bolide.co.uk