I think you're missing something here in regards to a media server. First, check out this software for your Mac,
http://wiki.plexapp.com/index.php/Getting_Started It can basically turn your iMac into a hub for a media server. Then, all you have to buy is an external storage hub to store your media on. I'm not exactly sure how much storage you're looking for but check out sites like New Egg and Tiger Direct for cheap prices on drives. Buy an external raid enclosure, load it up with cheap drives, and have some fun. Of course, you could always look into a Drobo at the prices you've mentioned.
I too have looked into the Samsung player and the comparable LG player as well. I think I'm going to wait till the next generation at this point. Having Netflix built in is a great feature that is inline with where the industry is going. I think it could be a good compliment to a media server, not a replacement.