All depends on personal preference and also budget.
Alpine,JBL,Audiobahn,Pioneer alldo great sounding subs.
Again Alpine,JBL,Audiobahn,Pioneer,Jenson,Vibe,Kicker and so on do great amps.
And for speakers there is loads of choice depending on what your after?
Have a look here www.bassjunkies.com to give you an idea of prices etc.