I am in a like situation right now. :)
What decision have you made?
You could use the SPs with a framework like iBATIS, I don't know enough about hibernate/jpa to comment regarding those frameworks.
We are doing this in 2 projects, one uses IBatis mapped to POJOs, and the other uses Spring-Jdbc mapping to java.util.Map, so far I feel that Spring-Jdbc with its JdbcTemplate is more comfortable, specially if your project is small, but IBatis is more maintanable if your project is big, both play nice with Seam using Spring as bridge.