Boxster S Anniversary model. 2004 registration.

[Silkmore]

Hi, My Michelin Pilot rear tyres need replacing. The front Michelins are OK. I use the car mainly for track days. Its been suggested I use NangKangs instead of the Michelins. There is a cost saving but I wonder if it is sensible to have different makes of tyre front and rear. Also how well do the NangKangs wear? The Michs have done about 20 or so trackdays and were not new when I got them so they seem to wear well.
Any thoughts/comments welcome.

[88racing]

You got 20 track days out of a set of road tyres? Not pushing on much then?