New Drives Or Upgrade Bravos
 

Ive read all the old threads I could find, but would still like some opinions on whether to upgrade my current Bravo I drives or purchase new (used but better)
Have seen Max Machine Worx and Billett Marine thrown around as upgrade sources but have no idea as far as $$$ and what is done. What will be the most cost effective way to do this and what will hold up the best. Im repowering from current 500efi's to probably around 600hp. The boat weighs approx 8500lb and is mainly used on the Mississippi River which means its rarely out of the water. Dont care about hole shot, and its always babied coming onto plane. What are the best options for reliabilty and trying to be somewhat cost efficient?