It's better to say: "I would appreciate it so much if you could reply at your earliest convenience." or "I would very much/greatly appreciate a reply at your earliest convenience."
"I would be appreciative if you..." this is correct though, just more "passive." (and I would leave out "so much." "appreciative so much" is a strange placement.)
When you say "I would be appreciated" it means that someone else would be appreciating you rather than you appreciating someone else.