I use the Omni MP170 epoxy primer and the Mp282 high build primer. Both of these are half the price of the Dp40 and K36 primers and work just as good.
For whats its worth it is probly easier to go with a base/clear system if you are going to wet sand and buff it any way. I would get the DBC base coat as the omni doesn't cover as good and it will cost the same in the long run.
I buy my stuff at Finish Master and they sell Zolatone and Transtar clears with both work good and are under a $100 a gallon.