for rap and music with a lot of audio engineered bass I would go with a 12" sub with more airspace, or a bandpass or ported box. Gives a deeper, looser sound.
For more all around, rock, music with kick drum and bass from the guitar, like rock smaller subs, like 10 or 8s in sealed boxes sound better. They are tighter, and more punchy sounding. I have a 10" kicker cvr running off a 1200 watt sony xplod amp. Works for my all around music. I can turn the sub up from my head unit if I want more bass for rap or turn it down for rock, or even country. I need to build a box with more airspace however.
As far as sub choice, determine a budget, and then I prefer kicker, alpine, or even powerakoustik. Kenwoods and pioneers are probably pretty good but I dont have much experience with them.
2003 Black Ford Ranger Edge
2 Door Ex Cab
3.0 4.10 8.8 LS