A friend has this Creative Sound Blaster Live! 24-bit External Sound Card click here, & is quite satisfied.
Check if the Trust is also 24-bit - don't get anything less if you can afford it.
If I had a choice between Creative & Trust, I'd choose the former every time.
Some more external Creative ones to choose from click here (prices include delivery, which is free).
Yet more USB external s'cards (sorted by ascending prices) click here (click the 'Detailed product information' to see more info of each card). You can use the 'Compare' feature to see how they stack up against each other.
Also have a look on eBay - filtered to Creative external click here - you could pick up a bargain.
Remember to get a 24-bit s'card if you can afford it. Good luck with your purchase. G
PS - If you purchase from my first link (Amazon), beware - they may send you an INTERNAL PCI s'card - happened to my friend twice for the same transaction!