Rick i really dont think it makes a big difference. the main problem I have with the Minwax is like you said it is
OIL based. then I think about the paint going on top of it and whether it will stick or not. I have heard of guys useing it and says went on great I just have not heard of the after reports of how well the paint adhered and if it did how long it lasted.
Joe
PS on my tips page
http://home.mchsi.com/~jahuntley/help/help.html#Tip 8 there is a huge list of places to buy it. maybe you have one of them stores by you that may have it or you can try the oil based and let us all know how it turns out. Poly is Poly it is just the base that matters