Importance of Cap/Resistor type

[Dwiel]

Hey, I recently built a small headphone amplifier for my 600 ohm headphones. I ordered 'audio' film type capacitors, and the amp does sound very good. However, I am wondering how important using the fil type capacitors is. The ones I have are very large and take up about 1/5 of the volume of the entire amplifier. I have two of them and they are about 2cm by 1cm. I used standard electrolitic caps in the 'power supply' (turns 0;+9v to -4.5;0;4.5 v) and I cant hear anything wrong with the amplifier. I am not sure if maybe I replaced them with better ones I might notice a differnce...

So, How important is the capacitor and resistor type in a chip amp like this?

BTW, I'm using the shematic from here .

I am thinking of replacing these big caps with some smaller ones but didnt want to waste my time if it would ruin the sound. Also, I was gonna make one of these for a friend, and I figured that if I could design it using smaller parts, we could fit the amp into a much smaller enclosure, which is fairly important.

Thanks