Yep- honesty is the best policy for Job A, I reckon. The best thing to happen would be if you get an offer for B, C or D in the high 60's - then I'd call company A toute suite and tell them that you have an offer at that level. That means that, if they haven't put out the offer, they can revise it (if they want) before they send it to you. Also, telling them that, all things being equal, you'd like to join Company A will be a good thing and will create warm fuzzies. For me, if Company A offered e.g. €65k and Company C offered €69k, I'd probably go for Company A if that's the one you're most interested in.
I find that people are happy if you give them as much honest info up front - so if you get an offer from Company C at 69k and Company A at 60k, just let them (Co. A) know that you have a higher offer at 69k and you are keen to join company A and ask then if there is is anything they can do about their offer. I'd be surprised in those circs if they wouldn't raise it by a few bob.
Good luck with it - sounds like the interviews are going well!
Sprite