If it's going to be used for TV/surround sound then I would first ask where are the speakers located in relation to your sitting/viewing area. Make sure they're located halfway decently so they act as they should. If they aren't and it's primarily a sound system, the following isn't so true.
Your surround speakers are primarily for smaller "less important" sounds. This will usually be more background noises than main focus noises (think rain, or crowd noises in football games, plane flying by etc.). Since they are not your primary speakers, if you're on a budget this is the area to save on. Your center channel is going to be where most of your dialog comes from. Make sure you get something that performs well in the vocal/dialog range (roughly 100-1,000Hz). Your front stereo speakers are arguably going to be your most important. You will get a bit of everything from these and this is where I would get the best speakers (followed closely by the center). Pretty much everyone knows about sub-woofers, they're filling in the lower part of the frequency range that's missing from the other speakers. Personally, I think there is negligible difference between 5.1 and 7.1. If you're budgeting, skip the extra 2 speakers and run 5.1.
Finding good speaker recommendations online without audio equipment to set it up is six of one and half dozen of another. You're going to get recommendations from all the major higher end companies (Klipsch, Bose, JBL, etc.) and they'll all sound pretty decent. Find something in the price range you like and go buy it. Unless you're going to start getting frequency response charts and trying to lay something out it's all opinions.