It depends. How far are you throwing your DX Leopard? Are you seeing significant high speed turn from it? Is the DX Leopard new or beat?
My knee-jerk reaction is that you should be throwing the DX Leopard until you can routinely get it past 275'-300'. At that point, a beefier Pro Leopard (or an even beefier Champ or Star) might serve you well.
Be forewarned though... the Champ and Star Leopards are SIGNIFICANTLY more overstable than a decently worn DX Leopard. You might question why they even have the same name. I have some new-ish Champs and Stars that resist turn when I put them out past 350'.
EDIT: I'm glad to hear you are throwing the Leopard. It is a great disc to start with and still remains one of my favorite discs even though I've been playing for 20 years. Its very versatile and remains relevant after your skillset grows.