The best is to go for DB2 9.5
There are two options to get this upgrade:
a) Go through the proper migration process - which means you have to go though 7,8 and then 9.5 (Check documentations for exact details)
b) Create a 9.5 database, export from v5 database and import to 9.5
Given you have to go through a few versions, b seems to be a better option.