There is no doubt that crossbows will meet your need for speed no matter whichever brand and model you choose but the best crossbow for hunting will meet it more effectively. It is all due to the better design, quality of material used and better functionality of the entire mechanical device that produces a flatter trajectory. If the arrow has a flat trajectory, then you will have a better prediction of arrow drop. You will be able to calculate the distance better and make a good shot. This is not possible with heavier and slower speed arrows.
Science and stats
It is all about physical science and dynamics. For example, a 400-grain arrow from two bows if sighted from 20 yards and one is shot at 300 fps and the other at 350 fps there will be a difference of 2inches at point of impact 30 yards away. If the point of impact is 50 yards then there will be a difference of 8 inches or even more. These are not computer simulation result but tests conducted in real situations. Each test was done using the same bow that zeroed at 20 yards. In extreme cases, a 370-grain arrow will drop 20 inches or so at 50 yards as compared to 30 inches drop for a 545-gain arrow.
How much energy needed
The energy measured in these arrows is kinetic energy and there are specific requirements of each bow and arrow type to make an effective kill. With 25 foot- pounds of energy with your arrowandbroadhead setup to hunt small game of rabbits and groundhogs. With 41 foot-pounds you can hunt medium game like a deer, with 65 a black bear or wild boar and above that the toughest game like Cape buffalo and grizzly bear.