Don't go by looks.. Both are same speakers.. exactly same sub, and same satellites. But X-540 is newer, and has remote and matrix mode. I think its worth the money.
If you are very tight on budget (or are a Creative fanboy

), have a look at
Creative T6060. It has 8 Watts RMS per channel (4 channel), 18 Watts RMS center channel, 22 Watts RMS subwoofer thus making it a 72 Watts system.
For comparison, X-540 has 7.4 Watts RMS per channel (4 channel), 15.4 Watts center, and 25 Watts subwoofer, a total 70 Watts system.