If you split it up you will make more money total, but it will be more work to sell it. I would suggest taking out the SSDs and the 640GB drive and only lleaving the 320 GB. Also keep the blu-ray drive. People are not going very much extra for the blu-ray or the SSDs you would be better off just saving them for your next system. Overall I'd say expect about 500-600, but you might get lucky.
I would say $800-900 but you might have trouble explaining to most potential buyers why that computer is better than the ones at WalMart. Most people don't know what an SSD drive is and why they should pay extra for it.