Well if you want you can always take the upgrade path 12.04 > 12.10 > 13.04. I had to do this because the is no alternate installer for Ubuntu after 12.04 LTS. Not even the server installer recognizes my RAID 5 configuratioin. Guess, like Fedora, they don't make installers the way they used to. 
If you do a minimal install this doesn't take as long as you might think.
Take care