Unfortunately it's very hard to tell how good a piece of A/V gear is going to be by looking at the specs. The numbers can be generated in different ways and w/out knowing how they measured don't mean much.
Generally speaking in a amplifier/receiver you want to see a power rated with all channels being driven. Inexpensive/cheap amps will have power rating in the 100's of watts but it's only with a single channel under load, during actually playback the number is much lower. Ideally you also want to see what the power is rated at under a lower impedance setting which is measured in ohms (Ω).
Ohms are the amount of electrical resistance that the amp has to work against to operate the speakers, most are rated at 8 ohms (the real number fluctuates during playback) which is sort of considered "standard". A good amplifier can handle a lower impedance and will often say so in the spec sheet. What you want to see is something like "50W: 8Ω both channel driven - 75W: 4Ω both channel driven" a lower impedance is harder for the amplifier to maintain current. If the number into a lower impedance is lower then you know the amp is already going all out doesn't have the power reserve to handle the lower load, it doesn't have the headroom to go anywhere. Another good sign is weight, good power supplies needed to deliver enough to the speakers have some weight to them, and I would shy away from really light amps (of course it could also just mean that the manufacturer stuck a metal plate in the bottom instead).
Ultimately the only real way to know what you're getting is to find a situation where you can audition the gear first and let your ears be the judge. Failing that you can fall back on reviews from reputable magazines/sources.
I don't have any first hand experience with Pioneer, they used to make some really good gear 20-30 years ago but as I understand it that's not necessarily the case anymore. Still that may be a good little integrated amp and work just fine for you. Do a little research on that amp before purchase. Personally I probably wouldn't go for the Pioneer speakers, there are a lot of good bookshelf style speakers out there at reasonable prices. Some good brands have been mentioned already like B&W, I would also add Monitor Audio, Polk Audio, etc. I own a set of speakers from a Canadian company called "Energy" (a division of Audio Products International, part of the Klipsch Group) and I think they sound pretty good for the money.
I found some listings on eBay;
http://electronics.shop.ebay.com/?_from=R40&_trksid=p5197.m570.l1313&_nkw=Energy+C100&_sacat=293Shop around, do some research & try to listen to as much as you can, your ears can tell the difference even if you can't quantify what you're hearing.
A friend and former co-worker of mine put together a website and blog that while meant for the A/V professional also does a good job of explaining a lot of the terminology and the how's and why's things work the way they do.
Ed's AV Handbook
