I always like to get pre-approved through my credit union or bank, which ever has the best rate at the time or idealy have cash in hand, don't think that will ever happen for me. Have a good idea what the unit is worth to you before money is ever discussed. If there offer is close I will do the whole song and dance with them if it is not than I give them the price I an willing to pay and walk.
They key is what it is worth to you. Two units of the same year with the same features are not necessarily worth the same amount.