It is hard to properly evaluate speakers without hearing them first. IMO, if you can't demo them, the next best thing is to read reviews from qualified listeners who have heard many different speakers (NOT your average Amazon reviewer).
A thing that I first look at in a speaker is what are its drivers and how are they configured? For instance, if you are looking at your center channel, is it a MTM configuration, or maybe a WMTMW configuration, or a WT/MW configuration, or something else? How large are drivers? What sort of tweeter is used? What kind of materials are used in the drivers?
The manufacture stated crossover frequency gives you a general idea how low the speaker will play. However, sometimes these values can be somewhat exaggerated. Something even more useful is a frequency response chart.
Certain speakers put more emphasis in the treble range (bright). Others highlight the mids/lows (warm). People may have an affinity towards one of them or neither of them (neutral). The driver construction makes a considerable difference on the sound. Some people swear by ribbon tweeters, others will pass on them all day. The best thing you can do is listen to a few different setups and figure out what you prefer. Not even the best reviewer can determine that for you.