headphones - do i need them?

[robawalsh]

on i-doser.com at the bottom it says 'Requires Approved Headphones' which is a link to some very nice, wireless Sennheisers, BUT THEY COST £70!!
I currently have the Sennheiser CX300's which are earphones but are very good ones for the price:

Frequency response: 18Hz - 21kHz
Cable length: Asymmetrical, L: 170 mm: R: 510 mm, (85 cm divider to plug)
Impedance: 16 Ohm
Sound pressure level (SPL): 112 dB (1 kHz, 1 Vrms)
Jack plug: 3,5 mm stereo (angled)
Ear coupling: intraaural (ear canal fit)
Transducer principle: dynamic

Firstly, how 'required' are they? cos if you look around on forums some people say they get effects from the standard iPod earbuds.
Secondly, will i get full effects using these earphones provided i take the dose correctly?

Thanks

[Tool33]

You don't need expensive headphones. But headphones/earphones are a must for I-Doser. I use some cheap earphones and they work fine.

[ChaoticShelly]

I have simple computer earphones, so as long as they block the sounds from the outside, they will do. No need for extremely proffessional headphones.