Your questions are more of a personal preference nature for most of us.
Some prefer a more quiet cruise (Corsa. which is approved by GM but is much
cheaper elsewhere) while others prefer a more muscle-car type sound (Magnaflow). These are probably the top two, although there are also exhaust products from other manufacturers in the fray.
K&N and Volant make complete CAI systems. Lingenfelter (LPE) makes an air box with a very large filter but no intake tube (uses the stock tube).
Personally, I use an LPE air box (w/stock tube) and Corsa exhaust.
I'm looking at changing the intake tube out for one of the aftermarket plastic units because of the flexibility of the stock tube under the heavier demands of larger cubes.