"Especially the 3750 range. I've heard people say that by adding another power supply in the switch you can increase the budget.I've got a 48-port 3750 and I may need to connect a lot of Class III (15.4W) PoE devices. Power budget of a 3750 is 370 Watts, enough for 24 Class III, but likely I'll need more."--from yahoo answer.
As we know 3750-X ( WS-C3750X-48PF-S ) goes to 800w. So,on the 3750-X pay attention to power supplies as that will determine the capacity/etc, the part# I referenced should have the correct PSU though for the full 48 ports. The 2960-S part number supports the 740w out of the box.If you want to know more about Cisco 3750 series switches, you can follow Router-Switch.com.
Cisco WS-C3750X-12S-S is an other famous used switch which provide IEEE 802.3at Power over Ethernet Plus (PoE+) configurations .