If you're only planning on doing one, an XY table and good drill press is probably overkill. Unless you're shopping for a drill press to keep for the ages already, and this is just the final spur to get one, don't overspend.

You need to keep in mind that the lower and jig stick up quite a bit from the vise/clamp/table, and you need clearance for the drill bit, so you'll probably need a lot more than 8" table clearance to finish a lower. Figure at least 16" of adjustability between the spindle and plane of the table, though a couple inches less might still work.

Be sure to plunge cut only and you won't overload the bearing in the drill press - it's not a mill and never will be, so even with a mill bit is not suitable for side cutting. With the drill press/jig method, you plunge cut with regular old drill bits to remove most of the material and finish with dremel and hand files. A mill bit can be used to get the fire control well floor flat, as they cut flat on the bottom, but again, don't try to get too fancy with side cutting, as a drill press is not made to handle those forces.