Hi Mon,
It is near impossible to suggest one stallion, there are so many high quality options available, but as you are taking one shot at breeding a future broodmare I would suggest that you do go with a proven stallion and one with an impeccable pedigree.
Art Major has been a great sire from day one - in Australia, New Zealand and USA. He is a lovely horse and he throws good looks, size and athleticism into a high proportion of his offspring. Just what you want in a broodmare. He is by a great sire in Artsplace and his maternal family is exceptional. He ticks every box so if you like him you should go to him IMO.