If you want to try it, go for it. Just make sure you buy the add-on venturi kit for the MJ1200. The venturi hose that comes with the skimmer does not work for skimming, you need this one:
I heard the MJ1200 fit if you cut a piece of of the box for the Excalibur. Never tried it.
To really make the skimmer scream, use a MJ1200 with no venturi, then add a Mazzei injector on the skimmer's intake pipe to make bubbles. A small Mazzei injector and fitting will cost you about $40, but apparently they work extremely well at producing fine bubbles for skimming.
The Rio 800 works good, and mine quieted down a lot after the first few days. Just something to keep in mind...
2x Sunburst Platys (2M, 2F) // 3x Neon Tetras (?) // 2x Cherry Barbs (1M, 1F) // 2x YoYo Loaches (?) // 1x Bushy Nose Pleco (M) // 1x Clown Pleco (?) //
-30# Live Rock
-Mixed Snails (Nassarius // Cerith // Astrea // Black Turbo // Mexican Turbo)
-8x Blue Leg Hermit Crabs // 1x Banded Serpent Star // 1x Cleaner Shrimp
-1x Royal Gramma // 1x Percula Clownfish
-2x Mushroom Leather // Metallic Green Star Polyps // Pulsing Xenia // Striped Xenia // Blue Mushroom
-Remora + Maxi-Jet 1200 // 2x Maxi-Jet 600 // Maxi-Jet 400 // Visi-Therm Deluxe 50 // Current USA Orbit 2x 40w PC