For music then, the T40s are an excellent choice. Due to the lack of subwoofer you don't get the flashy and explosive bass lines some people like, but it also means you get far better overall sound due to the lack of separation. With the wider sound offered by the extra drivers and the better low volume clarity, there's also a distinct difference between these and T20s.
Of course, music isn't the only thing you want speakers for, with films and gaming always important. This was one area where the T20s were merely decent rather than outstanding, but the T40s go some way to correcting this. Again, one must stress you won't get the explosive bass one would get from having a subwoofer, though it's conceivable you might like to use the T40s in conjunction with a sub bought separately.
In any case, the T40s are an improvement in both areas. Dialogue is more clear and defined, especially at lower volumes, while explosions and gunshots have more impact. Moreover, the wider sound produced by the T40s creates an immersive environment that's very satisfying to sit back and enjoy. Gaming performance is also impressive, providing plenty of oomph to effects and dealing with the subtleties of more atmospheric titles admirably.
As you might have gathered then, the Gigaworks T40 speakers are every bit as impressive as the T20s that came before them. For music, the 2.0 channel mix is ideal, creating a balanced and well defined soundstage with crisp and clear highs, great vocals and an overall sense of warmth and immersion. Bass isn't explosive, but that's to be expected and it would be churlish to compare it directly to a 2.1 set in this department. Indeed, the only real point of concern is Creative's decision to opt for a proprietary docking connection instead of a 3.5mm AUX input.
Thus, only two questions remain. First, should you buy the T40s and secondly, are they worth the extra outlay compared to the T20s? Perhaps inevitably there's no clear cut answer, because it rather depends on how you want to use them. If you want speakers just for desktop use, where you're sitting at a desk near to the speakers, you're probably better off with the T20s. They're not as large and imposing as the T40s and whereas they sound slightly cavernous when up close, the T20s have a closer and more intimate sound that's superior when you're seated quite close to the source.
If, however, you want something for the living room or for when you're away from your desk, then the T40s are the better option. Thanks to the wider sound they produce they fill the room more convincingly, while the performance at lower volumes is much improved. They're also better for gaming and films, with clearer dialogue and greater immersion too. Whichever you're intentions, both remain compelling options for those who want decent sound quality at a reasonable price.
Just like the Gigaworks T20s, the T40s are a superb set of speakers for the price. Excellent clarity and a wide sound makes listening to music a joy, bringing the subtleties of all kinds of music to life. Gaming and film performance was also impressive and if you want an inexpensive but high quality set of speakers for a living room, then these come highly recommended.