I'm, using 1050W of class a/b for my IDMAX....I always go with class a/b amps. I'm just partial to them.
People will argue up and down the differences in sound between a class a/b and class d amp on subs. There are many "reliable" people who strongly argue both sides of the coin.
Some examples....Matt Borgart from Image Dynamics is a huge proponent of only class a/b amps for all drivers. He hates Class D/T amps. Fred Lynch, the owner of the ID demo Passat, just switched from 4 D4 IDMAX's and 4 Arc Audio 1500s to 4 IDMAX D2's and 4 Arc 2500. Many people said that the difference was obvious. Jason Winslow, an IASCA compeitor, was using a JL Audio 500/1 on his sub (class D). He then swapped it out for a lower power class a/b amp, and had increased SQ.
Those three arguments are pretty powerful, as they are all industry people who have good experience.
If you look at the flip side, the JL audio demo vehicle (their GTI) had two 13W7's powered by 2 JL 1000/1's. Everyone raved about the subbass...some saying it was the best they had ever heard...with no EQ either.
I think it depends on your wallet.
A class a/b is much more versatile, and will put a bigger hit on your alternator. It's good for full bandwidth, so if you decide to expand your system, you can use it on something other then subs.
A class d is going to relegated to sub only detail, but it may have a subsonic filter (important depending if you are going to port and the music you play). They are a bit easier on your alternator and definitely cheaper.
One thing about those IDQ's - please, please, please port them!!!! Tune them to around 30Hz and you will thank me later.