IEEE802.3af, 802.3at @ 2 x 30 Watt. But now @ 2 x 75 Watts
I don't get how you go from 160W over 4 pairs to 2 times 75W. That said:

One of the issues with PoE is heat. I've heard various accounts of people having issues with cables going bad over time because they get warm and it ages the conductor. Sure, even if you go pushing 160W through a single cat5e cable, you are only going to be dealing with about 300mW per meter (based on the assumption that you have 24AWG copper, 48V at load, 40W per pair). But the thing is that these cables are often bundled up. The inner cores can't get rid of the heat, and even though it's only a very small amount of power, their actual temperature does run up high (think about it, if you have a bundle of 48 cables coming from a switch that 300mW is suddenly going towards 15W per meter, with the center cables having no way to dissipate the heat. And on top of that, if you are running an average of 50m to every load, you are wasting 750W of power! 

There is also the fact that PoE is designed for low-power loards: IP cameras, wireless AP's, phones, etc. If you are dealing with servers, you likely have acces to power already. Why would you want to run it over ethernet cables, that waste more power in the process, increase the cost of the circuits, ... 
On top of that, with fiber becoming more and more commonplace...