Which version of Solaris for my Sun Sparc system?

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http://serverfault.com – I'm about to buy a used Sun Sparc machine (Sun Blade 2500 Ultrasparc IIIi 1,28Ghz) in order to use it as a personal development server. Problem is, it is sold without any OS. I would like to install a Solaris system on it, but I don't know what I'm looking for. I think Solaris 10 should work, since it was released the same year than the machine, but I'm not sure. And could the newer Solaris 11 work on it? (HowTos)