Most future proof

[shokhead]

Would it be one of these or another? These should all be about the same price range.

[N. Abstentia]

The moust future proof one is whichever one has multiple HDMI, Component, and DVI inputs and does switching and upconversion.

It should also have a network jack.

Which..if any..is that?

[kexodusc]

They've all got pre-outs and multi-channel inputs, I believe. That's as future proof as you'll ever get with a receiver. If you really need to run your HDMI cables into your receiver, I think at least 2 of these have those as well.
None have the next generation Dolby Digital/DTS decoding that will come with BluRay/HD-DVD, so I don't know how "future proof" these are...but maybe a HD-DVD player with built in decoding could get around that.

Trying to future proof HT equipment is an uphill battle unfortunately. I suspect all of these would provide you with a few more years of enjoyment, maybe more until you decide you absolutely need the new DTS/Dolby decoding, 11.2, etc...