Fastest item dispensing solution in the game?

My mob farm produces a lot of items that I need dispensed (double chests and double chests full) and I want to be able to automatically dispense them by flicking a lever. Right now I have four dispensers running on comparator clocks, but that is way too slow, since dispensers only dispense one at a time. Is there a faster way to dispense items other than adding more dispensers? (on the server I'm on, hoppers transfer items a stack at a time, not one at a time, so I can't figure out how to make a good item sorter).

This is what I have right now:

Is there a faster dispensing solution, or even better, an item sorting solution where hoppers transfer entire stacks at a time?

Solution 1:

If a manual process is acceptable: Break the chests and place them again.

Something a bit more automated: Hopper minecarts. You can send them below your chests, two should be easy to do, four should be possible, maybe you can even stack many inside of each other. They suck the items out much faster. You can then send them elsewhere where they can slowly dispense items while your main storage fills back up.
If you have the resources to craft multiple stacks of hopper minecarts at a time occasionally, then you could also let the hopper minecart break on a cactus, which drops all the items at once, then retract the rail with a piston, quickly dispense and retract lava and extend the rail again. That would quickly delete all items, but also the hopper minecart. It seems to drop last, so catching it would not be easier of faster than dispensing everything normally.