Not all bookshelf speakers come in pairs. You have to be careful when ordering on-line to make sure you are in fact getting a pair verses a single speaker.
As far as brands, everyone has an opinion on that, but in your (and mine) price point probably the Infinity and Pioneer speakers are your safest bets....but, do a search on Amazon for bookshelf speakers, find the price that works for you and look at the reviews. Try bing or google and see if anyone has a video review on the speakers.
Another good place to start is Bestbuy (BB). Go and look at the speakers. Try them out. Pick up the speakers and feel the difference in weight/quality between a real speaker and the speaker that comes with a HTiB or receiver/speaker combo.
For some people the combos/HTiB work fine. I put in one (combo) for a co-worker (Denon with BA speakers - one day sale at BB from $599 to $299) and he is completely happy...but his small children (5 from 12yrs to 3yrs in age) use it, so a weaker system saves their hearing and lets the grown ups relax upstairs.
Speaker prices vary from day to day and sales are common. For example, I bought my Infinity P163s for $85 each and several days later Amazon dropped the price to $49 each, so I called Amazon and got them to refund $70 on my speakers. The moral is to catch the speakers on sale.
As I stated in my first post, I went with Infinities (fronts, center, rears $300). $300 - I bought a dedicated center channel for $110 (Infinity PC251) and all it is is the P153 with one extra woofer (5 1/4 inch driver), so if I was doing it over, I would save the $60 and just use a P153. Nothing wrong with using a bookshelf speaker for the center channel, but most (not all) will probably disagree with me.
I setup and tried out my new Infinity P153s (rears) last night with Armageddon (1998 movie) and Under the Dome (show). The speakers are worth $45 each and would make a great starter system by getting five of them. They are large and heavy, so that might be an issue for you.
I have the Yamaha 375 which I have seen from $169 to $249. I paid $200 on sale and what I like about it is the "self" setup feature. I plug in a microphone and let the Yamaha setup/balance the system to insure that the main seating area gets the proper amount sound from the fronts/center/rears.
Finally, Pioneer speakers get rave reviews and seem to always be on sale.