Besides the type of wireless connection, you need to think about what style of speaker you want. Smaller, battery-powered speakers (usually Bluetooth) are useful because you can take them anywhere, but they don't get particularly loud. Larger speakers generally offer fuller sound and richer bass, but they are typically more expensive and less portable. Besides single speakers, you can also find stereo pairs designed for desktop computers and home theater speaker systems like soundbars. These are obviously not portable at all, but if you want a centerpiece sound system for your living room or office they're likely your best choice.