After working on configs all last week for the 6500 series switches, I started to realize a pattern of wattage and capability...
so you need to be careful.
Assuming you are using WS-SUP720...
any of the family of WS-SUP720 or with additional cards like the WS-SUP720-3B andWS-SUP720-3BXL...
you will need to make sure you have at least 2500 watts of power.
 This is a minimum requirement.
  The issue comes down to what kind of electrical juice you can apply to the switch over all.
When using 110V electricity, a single power supply of 2500 watts (WS-CAC-2500W) only delivers 1300 watts overall.
 So on the surface, you would think it would work...
but no.
Here are some other power supply options for 110V: 2500 watts           WS-CAC-2500W                on 110V delivers: 1300 watts 3000 watts           WS-CAC-3000W               on 110V delivers:  1400 watts 6000 watts            WS-CAC-6000W on 110V, it has 2 inputs.
 If both are used, then you have:  2900 watts.
Instead of using the 6000W in low line mode on 110V, it makes as much sense has to have your electrician install a fresh 220V wall plug.
 Using the dual input scenario would take up your entire wall socket anyway.
The above is true for all normal 6500 chassis, no matter the size or whether a high speed fan is involved.
 There are other very specific rules for DC-powered supply units, depending on the chassis though.
Be sure that you're electrical supply line has enough amperage to cover the power supply too...
20-30 amp circuit.
Putting together a new switch configuration has alot more parts to it then just the blades.
 Hopefully, a little bit of planning can save you from surprises at install time.