Sounds like you're getting some great advice here from some real pros. A few thoughts from my decidedly less experienced view:
- There are some cheap portable router table alternatives that can be bought for $100-$150, but you still need a separate full-sized router to mount on the underside (the DeWalt will work for that) and they should be bolted or clamped down to a workbench. They aren't the greatest in terms of speed, accuracy, and ease of use, but still safer for smaller items like these speakers. I have one I use a couple times a year and it's been worth it. If I used it more often I would be spending the big bucks for a more "pro" solution like Mike Lundy mentioned.
- Direction matters. Moving the router with the direction of the bit rotation (called a climb cut) is much more likely to result in losing control of the router since it will want to run away from you. Moving against the rotation (standard cut) gives you far more control. There are some cases where a climb cut makes sense (like to prevent chip-out on solid wood), but not on MDF. The baseplate of the router should show the direction of rotation to help you know which way to go.
- A 3/4" roundover is going to take off a LOT of material. You might consider taking that in two passes. The first pass would be a shallower cut (perhaps 1/2" deep), then a full depth cut. You will have to deal with much less torque that way (especially if doing a climb cut) and it will be less likely to overwhelm your dust collection.
- On that last note, use dust collection, even something as simple as the dust collection attachment (which the DeWalt has) connected to a shop vac goes a long way. Also, wear a mask, goggles, and ear protection. You want to be able to see and hear these speakers when you are done.
Finally, please don't let folks like us deter you from doing this. I feel like once you get the router in hand and try a few test cuts you will start to get a good feel for it as long as you follow some basic safety precautions (secure the workpiece with a clamp or mat, both hands on the router,etc). My routers have proved far more useful for multiple projects than I originally thought. A quality router like the DeWalt will give you a lifetime of use, or you could turn around and sell it on Craigslist to get some of your money back if you know you will never use it again.
Good luck!!!
