What is the latest good lightning protection for a network?

You can check this,

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=pnet1gb

Look at this solution:

http://www.l-com.com/surge-protector-cat6-data-line-lightning-surge-protectors
https://www.ubnt.com/accessories/ethernet-surge-protector/

Also note that every time, you use a solution like this, you are running a risk or deteriorating ethernet signal.

I see that these protector units are in series relative to the ethernet signal.  I assume that the power rating they mention refers to the power of the equipment being served by the ethernet cabling, NOT the power of the lightning strike.  This did not seem to me to be clear in the documentation.  But maybe they thought the answer to that was obvious.  So how do I determine the power draw of an ethernet load?  The power draw on the line voltage is easy... the specs of the equipment will indicate its power, or at worst I could put an ammeter in one side of the line.  But the ethernet is using 8 lines of high frequency.  How do I know the power rating?  

And here is a more practical question... could I buy one of these units and put it, say, between the modem and the router and thus give protection to the entire system using one protection unit?  Or does each device in my network, like the client computers, need one of the protectors?

Yes, we already have some power surge equipment for in the AC line and we plan to get more.  So we are caring for that part of the picture.  We recently had a lightning strike which did considerable damage.  Evidence shows that damaging strike came from both the AC line and also the phone/ethernet.  OK.  Our internet signal comes via a standard telephone cable, not fibreoptic.  There was some lightning protection on the incoming phone line.  Even so, there was damage to some of the phone equipment.  And perhaps the other damage that we experienced in the network may have come from that source.  Our ethernet switch blew.  

What about my power question?

Sorry, I don't know the answer to your power question.  Take a look at this article as I had it bookmarked a long time ago:

http://www.ti.com/lit/an/snla089b/snla089b.pdf

OK, well, in the URL you gave me earlier...

http://www.l-com.com/surge-protector-cat6-data-line-lightning-surge-protectors

What exactly do they mean by Power Rating, and how is the consumer intended to use that information in selecting a product to purchase?

This sounds like some good advice, but I have not actually tested it.