I was in the middle of listening to the Big Mom's Concert Album, and suddenly found myself researching Shiro Hamaguchi accredited soundtracks (once again in my life; even though I think Kohei Tanaka is solely responsible for said Concert album), and saw, "Heh, his first major work of original compositions was the video game Ehrgeiz, I never knew that! I had a friend really into that game, so I should really look into the soundtrack and feel what he felt all those years ago."
I looked for YouTube videos, even started listening to some of the video game Ehrgiez music, and wondering why the titles were completely different. Anyway, it's the anime with the same name, that Shiro H. worked on. The first few in the following ZIP file have extremely strong similarities to One Piece music. Currently listening to the rest, am sure there will be more strong ones in there. (I found the whole OST on ffshrine forums, but only included SH's contributions here.) Anyway, enjoy your favorite style of music, but different, and two years before One Piece:
http://www.escaprism.org/songs/Ehrgeiz%20Anime%201997%20-%20Shiro%20Hamaguchi%20tracks.zip
edit: last track very good
(accidentally left 1 track in from a different composer, Akifumi Tada, solo. "S.A.C." [the collaboration with someone and Shiro Hamaguchi, unless they each did one section?] is very good, too, so maybe this other composer is good as well…)
edit 3: http://www.escaprism.org/songs/Ehrgeiz%20Anime%201997%20-%20Shiro%20Hamaguchi%20tracks%20-%20ultra%20select.zip Whittled them down to 4 tracks. Superb listening loopage!