Gregg Berger was the voice of Cutter, Firefly, Spirit, Ripcord, and Sparks in the Sunbow G.I.Joe cartoons. He's also credited as the voice of "Moon Viper" - but we're not exactly sure who that character is.
The first clip below is of him as Cutter - which is probably the most like his natural voice - then as Firefly. The second clip below is of him as Spirit. The third clip below is him as Firefly introducing YoJoe.com.
A few of the many characters Gregg Berger has voiced include Cornfed from Duckman, Grimlock from The Transformers, and Odie from Garfield.
Thanks to Gregg Berger for graciously lending his voice to YoJoe.com.
Neil Ross was the voice of several characters in the Sunbow G.I.Joe cartoons, including Buzzer and Monkeywrench.
This clip is of him explaining his most famous G.I.Joe character, Shipwreck.
Ross has lent his voice to many cartoons, including Voltron, the Transformers, and the Centurions.