So the problem with most TV's for streaming via Network is that they require a DNLA server, making it necessary to run Twonky, TVersity, or something else. I had to do this and I don't like it as it eats up system resources unless ofcourse you have a server of your own that does this exclusively.
The external drive connected to the TV could actually work. However not sure if you can get the little box to connect to the network and USB at the same time. If you could that would be ok. Acceptable I guess.
Personally I've found the best way though is with a NAS or Internal Raid and shares that you add to XMBC on the Apple TV2 (Jailbroken). It's simple, easy and has a ton of developers working on it so it's really always improving.
I also have a Quad Core PC connected to the TV which works really great for tons of things. Video Skype, Browser, Amazon Prime Instant Movies, Games, Movies (XBMC Windows), and the list goes on. Just make sure you get a good wireless control system. I think the keyboards with the attached touch pad mouse is best since it's all in 1. But you might want the mouse for gaming. I the machine for racing games which I use an XBOX 360 controller with the Windows Wireless integration.
HDMI & DVI are essentially the exact same signal just different connectors. There is no conversion between these two plugs, so you can get DVI to HDMI and get 1080p np. If you want to step it up go DisplayPort.