well, digital_paladin as u said in ur earlier post that music is ur main priority therefore you can go for 2.1 speakers and altec lansing CS21 gives amazing music performance and is best suited for ur budget wherears if you want to go for lower budget speakers than as cvvikram said, u can go for altec ATP3, they are the best speakers available below 3K
on the other hand logitech x-530 is an above average 5.1 speaker set and cannot match altec lansing cs21 in terms of bass and sound depth....the truth is that there are no 5.1 speaker sets below 10K which we can consider as a good performer though you will definately get average performing speakers like logitech x-530, creative inspire 5.1, altec lansing vs3151(which i guess is discontinued now), so the fact is that there's no point in going for these kind of speakers as they dont offer too much in terms of audio quality...
the cheapest 5.1 set which i consider as a good performer and offers good audio quality is logitech Z-5300 which is available for arnd 11-12K
so if you want multichannel sound and there's a scope for the expansion of budget than go for these speakers otherwise stick with your current budget and go for altec lansing CS21...
ENjoy...
