You choose speakers "horses for courses", which is to say, speakers that best meet you requirements and simply, sound best to your ear. Bookshelf, Sub/sat, tower, panel are all viable options in your price range. Most speaker companies have series within their line, good, better, best; bronze, silver, gold; premier, elite, limited. If you have a big room and like loud, then that will guide you to a big floorstander, like a JBL S3900 or 4367 rather than a small bookshelf. Conversely, one of the nicest systems I've seen recently was in an 11X14 spare bedroom and consisted of a pair of KEF LS-50s, a driven by a Marantz 40 Integrated Amp. I love Magnepans, but you have to have both a Magnepan-friendly room that allows you to get them several feet away from both back and side walls and a very beefy 4-Ohm friendly amp.
In between you have the dual (or triple) 6" and 8" 3-ways. These are about as generally satisfactory of a speaker design as there is for your 'average' 200-300ft2 listening room, and from under $2,000/pr to well over $20,000 per pair they cover every budget point. They all have maximum output levels of aaround 112-115 dB and sensitivity usually 88-92 dB@1W/1M. They very dramaticlly in driver design (paper, kevlar, metal, composite sandwich) and tweeter (fabric and metallic dome, horn, AMT) and in cabinet construction (Vinyl MDF to cast unobtanium) and in internal bracing and detailing. But, the basic architecture remains - 2=3 woofers, midrange and tweeter in a vertical array. The reason is that this blueprint works very well across a huge expanse of requirements. How they sound varies as much as the pricetags, and some of the best values in audio fall into this category. From the the Polks and Monitor Audio SIlver 300 and 500 7G, to the megabuck Magico and Estelon and Watt, as well as B&W, KEF, JBL and a hundred more manufacturers.
Once you have you basic requirements, then comes research and education (read what people say, and learn to read between the lines) from which you create a shortlist that you can seek out and listen to and make your decision.
