2000 Crew Cab SE Subs?

I would say it definately depends on your tastes and the quality of the subs. You can get a 10" rated at 500w or 100w so that comes into consideration too. I think 3 8" subs you would feel more because more air is moving, but a quality 12" could hit some lower frequencies and save space. Also ported/sealed boxes have an effect on the sound aswell. You can get a single alpine 12" rated at 1500w rms I'd go for one of those in a sealed box and hit the lows hard.

Edit: Then again I have more space in the cab.

8's will do fine for everyday listening if its all you can fit. I listened to my system loud for a few months and now im over it, it hardly sees over 50% power unless im being an *** on purpose at stoplights :]. The 10" in a ported box just doesn't hit low enough, good in the 50-80hz range though.