it looks like it was a nice system when it was new. I bet you paid a bunch for it too. unfortunately its 2 or 3 generations behind technologically. I would say maybe $500 tops. the only reusable parts are the case,PSU, DVD and the HDDs as secondary storage. the X-Fi card is cool, but on-board sound has come such a long way the sound cards are now for the Audiophiles only.
$350 is probably what you will get out of it.