This dust cover is really good. The best thing is that it protects even the bottom when you are moving the sub on wheels and so it protects all the inputs and outputs! The top part is reinforced to protect the grill so even touring with this thing it's ok. The pocket in front is a nice detail but I never use it.
There are countless different cheap alternatives for this cover, however, based on reviews from others I decided to fork out the extra for this one. The cover is well built, with a solid board built in to the top and padded sides. This provides all the the protection you are likely to need for what is essentially a big plywood box. The side pocket and bottom flap are useful additions for storing cables and protecting the plugs from splash from casters (in the wet).