I have a 2000w amp and 4 - 12" Kicker speakers - can these be installed in one box and if so, what size box recommended?

i would use a ported box my cousin has a 2000w amp and 4-15"kickers and it hits hard

the first thing you should check is the compatibility,

check your amp, it should say how many ohms (can go from 2 ohms to 16 ohms)

then check your speakers ohm value if they match continue

i would never recomend putting an amplifier inside a box without any air circulation if its not made to do so.
amplifiers heat up fast if you play them loud, so putting it inside a box with no air circulation will only make its life shorter

also, if your amp only has two outputs check this site to figure out how to plug your speakers http://www.termpro.com/articles/spkrz.html

You need 4.5-6.5 cubic ft of enclosed space.  No port or venting.

I guess you really want to hear that ipod don't cha.

Depends on the speakers to a large extent. Wo-cha got ? 

Steve