Easiest way is to add power to your OE speakers (many people add a H/U), and to get a subwoofer to take care of the lows, while the speakers deal with the mids/highs. You don't need to go crazy with the subwoofer; 300W is more than suitable for the task of having your music loud enough to jam to, while not subjecting everyone else around you to it.
Try that for a while. If that isn't sufficient, then start looking into a set of 6.5" components to go in the front doors, and an amplifier to power them. A popular setup (and one I run) is to pick up a 4- or 5-channel amp, and run the front speakers of Ch 1/2, and bridge the rest for the sub, leaving the stock speakers powered by the H/U. Since they're just fill, and can ruin your staging, most people either leave the rears stock or pull them completely. If you buy a mono amp for the subwoofer, just sell it for a slight discount once you get the 4-/5-channel one.
As for the speaker brand, that's very subjective. Your best bet is to hit up a local audio store with a wide variety of music you'd listen to. Listen to your music on all their display options, and choose the one that fits your ear best.