[Earl34]

I was wondering if this was a strong enough amp to power my old Sennheiser 410's? I think I read that the Nominal Impedance(No idea what that means) is 600 and I'm guessing that my Ipod wouldn't have enough power to do that so I knew I needed an amp and this one looked good.

 

[NA Blur]

The airhead will power the 300 Ohm load of your HD410 headphones fine.  It may not be the best amp for them, but considering it is a small portable amp that usually runs off of batteries it should do fine.  I really recommend you purchase the not included power supply.  The amp runs well off of batteries, but does sound a bit better running off of wall power.
 
The HD410 has two 600 Ohm loads wired in parallel giving a nominal impedance of 300 Ohms.  The impedance of a headphone, or anything measured in Ohms, almost always represents how much the unit will tend to impede the flow of current.  Impedance also plays a roll in how much power is used by a device.  This is shown in the the general power equation below.  Many headphones use dynamic drivers where a voice coil is implemented.  This gives rise to impedance not only being used to calculate power, but how much current is going to be flowing through the voice coils.
 
V ( voltage ) = I*V
I = current in amps
V = voltage in volts
 
P ( power ) = I^2*R ; constant current source
P ( power ) = (V^2)/R ; constant voltage source
 
Where R is the resistance measured in Ohms. 
 
Ohm's Law
http://en.wikipedia.org/wiki/Ohm's_law
 
Headphone Impedance
http://en.wikipedia.org/wiki/Headphones