What is the size of your database?
Do you have 80+ RAID10 volumes?
You're good with the tempdb files. Start with 1/4 and add up to 1/2 (the number of cores) if necessary.
This survey is pretty good - http://www.sqlskills.com/blogs/paul/files-and-filegroups-survey-results/
Regards,
Igor Micev
Igor Micev,My blog: www.igormicev.com