Hi there,
I'm the bloke who sold you the Amber Ant. It is a fine little headphone amplifier but you can't expect it to transform the sounds from a very low end source to decent hi-fi sound. As the old maxim goes "garbage in, garbage out." I have a set of Audio Technica W5000s and a set of Sennheiser HD650s and use a Graham Slee Solo headphone amplifier. The problem with owning such high end gear is that it reveals so much sound from the source. I find listening to poorly recorded or music from a poor source unpleasant as my gear reveals any flaws present in the source or recording.
Re. the Graham Slee Solo. It's an excellent headphone amplifier. Sennheiser used the Graham Slee Solo to demonstrate the HD650s. It's received very enthusiastic reviews internationally. Within it's price bracket (around £350.00 now), it's regarded as one of the top four or five headphone amps available. I'm very happy with the Solo as I was with the Amber Ant. I use my W5000s most of the time for listening to music, games or movies but these cost over £500.00 in the UK so my priorities and choices are probably untypical here.
To the original poster here I would suggest that if you don't intend to amplify your 'phones you should look for a set of low impedance cans, i.e., Audio Technica, Grado, Goldring and some Sennheisers amongst others. These will provide tolerable sound direct from your soundcard or from a source such as a DVD player, Ipod, etc., without a headphone amplifier. But don't waste your money on Mickey Mouse so called "5.1" or "surround sound" headphones made for PC gaming. These tend to be little more than badly engineered toys. If you listen to music, I'd also avoid wireless headphones. A couple of years ago I auditioned a set of Pioneer wireless cans price at around £300 and was distinctly underwhelmed by them.