stock front speakers are 5.25", the hole is big enough with the right adapter for a 6.5".
pioneer, kicker, and polkson are good brands to go by... If you spend $100 on a set of one of those brands, you'll get good speakers. Besides that, it depends on what sound you're looking for. If you don't want to eventually install an amp and sub, look for something with a low frequency response range. I have 45 Hz - 21 kHz, and they have just the right amount of highs and lows.
I have kickers up front, 45 RMS wattage.