My brother works as an audio engineer and he says these are about the best you can get for amateur budjets.
http://www.dv247.com/studio-equipment/alesis-m1-active-520-active-studio-monitors-pair--30394Subwoofers are an audio false economy. You might get alot of bass out of them, but you're not actually getting a real good depth of frequencies. If you actually isolate each speaker, all you're getting from the subwoofer is dull thuds, and all you're getting from the little speakers is the same tinny shit you get with a $10 pair of budjet shit, though brought together they can sound somewhat passable.
There really is no substitute for size when it comes to good speakers. The size of the speaker is directly proportional to the range of frequencies it can (clearly) produce at one time.
Granted, most people can't tell the difference between a high grade system, and something thats just made to sound like a high grade system, but if you really care about sound quality, specifically for music listening, you want a good quality pair of active monitors like the ones I linked to, with a decent speaker size and a decent amount of power drain.
If you just want cinema style booming audio, then .1 subwoofer systems are great. Logitech are generally for the gaming / home cinema crowd, who really don't want much more than something that sounds impressive.