Speakers are a hard thing to rate because different people will have different expectations for their computer sound system. Some people only need basic sounds, like Windows midi clicks and beeps, or playing the occasional video online. While others may want to immerse themselves into the surround effects of gaming or listen to concert style audio. In the end you should really decide on the type of system you will want first, and then shop for the best model or brand that fits your price.
As for the 2.0 speaker arena, and how the Hercules XPS 40 Slim stacks up, well I've heard better and I've heard worse. One of the best 2.0 systems I've experienced has been the HK19.5 from Harman Kardon. There just seems to be no substitute to larger enclosures with tuned bass reflex ports when it comes to fullness of sound. But considering how small and slim the Hercules XPS 40 speakers are, the sound they produce is relatively good. Being so compact allows them to fit almost anywhere, and the remote module gives the ability to tuck them out of sight while still retaining control over volume and input/output. I also like the addition of the line-in port on the module, a feature that not many other systems offer.
I found the Hercules XPS 40 system available online in the $25 to $35 range, which is comparable to similar systems from other brands. The Logitech R-10's for example cost a mere $10, so you might expect the Hercules to perform better, which they did. If you want a fuller sound, with better low frequency bass response, I would suggest saving up for at least a 2.1 system. But if you're looking for a small footprint and low cost, without sacrificing too much sound quality, the Hercules XPS 40 2.0 Slim may be just what you need.