Thank you for your reply. I decided to connect an old pair of Sony bookshelves I found in the loft and, from what I can hear, they're a slight improvement over the satellites. The crossover frequency is way too low for anything other than highs to be produced by the bookshelves. So, in this respect, they're very much like the satellite speakers. However, although they don't produce mids very well, the highs are a lot better due to the tweeters. I can hear stuff in songs that I've never noticed before. It's great--well, not great, but an improvement nevertheless.
I'd like to buy a better pair of bookshelf speakers without breaking the bank. I don't want to spend more than £60 really because the improvement isn't really enough to justify any more. Also, they have to be pretty small to fit on my desk. The Sony ones I'm currently using are 220mm deep, so I'd like a pair either the same size or smaller if possible. Do you have any suggestions?
Also, is this likely to damage the amplifier at all?