The Samsung will be your best bet. But it really depends on the connections you are using for all these items. If you have HDMI for your Blu-Ray, 360 and your HD Box, those will all be fine. But you will most likely be out of luck on the PC side. After a quick look, I didn't see anything about any other connections on this thing.
Here are some threads to read on the unit:
http://www.avsforum.com/avs-vb/showthread.php?t=1234205
http://www.avsforum.com/avs-vb/showthread.php?t=1243655
It's a shame you are tied up to Memory Express. If you could find someone to buy the gift cards off you, I'd say get something like this, under $500:
http://www2.visions.ca/Catalogue/Cat...productId=6181 Very basic setup. While technically a HTiB, it's quite upgradeable. And you can most likely get the PC hooked up depending on your connections.