I wouldnt waste my money on donny gp now. It can actually work out quite reasonable taking in a foreign leg if you split a car with mates etc and get a cheap flight.
My money would be on sepang. Not as expensive as you think flying to Kuala Lumpur if you catch it right and it could be a nice little break (adding on a city break or even a trip over to Langkawai with the missus!).
And then theres Laguna - linked in with a trip to San Fran..excellent !
Otherwise Mugello or Jerez..
Nat