http://therecordingrevolution.com/2011/02/09/the-ipod-earbud-test/
An article which examines the final listening enviornment (sadly) of most recorded music, the iPod earbuds.
Addition:
While many people I’ve spoken to about this particular article have agreed with the sentiment of checking on many systems, it seems that good speakers & headphones are 90% of the way for most AEs. Personally I’ve only just started to use other systems to check my materials – simply because I feel that it’s a great habit to have. Especially when I don’t have 3+ sets of main speakers!