Eduard (www.eduard.cz) is a Czechoslovakian company that makes photo etch (PE) parts. These parts are paper thin and made out of brass. They add a lot of detail to some kits that aren't well detailed. If the 3 kits you list above are Tamiya kits, the Leopard 2A5 doesn't really need it. That is one of the nicest modern armor kits available. If it is the Italeri kit, the choice is yours. If the T-34 is a Tamiya kit, no PE in the world is going to accurize it. There are several better kits of a T-34/85 on the market that would run less than the cost of the Tamiya kit + PE. Gepard is an older kit as well so again the choice is yours.
Go to the Eduard site (see above link) and search for the PE set for your kit. You can then access the instructions for that particular set to see if it would be of help to you.