Headphone Recommendation

[lordbazzer]

Hi, new Core 20 user here. I'm using a set of Bose Ae2 headphones at the minute but they seem a little quiet even with the volume cranked right up. Looking at buying a better pair such as one of the Beyerdynamic offerings but I want to make sure I buy a pair that give me some decent volume. Most come in 3 or 4 different flavours of impedance- 16, 32, 80 or 250 ohms.

Can anyone help me work out which pair is best suited to this amp for maximum volume efficiency please?

Thanks.