Class D Amplifier(s) for SWARM Subwoofer System

Hi All.  I've got a SWARM subwoofer system (4 8ohm passive subs powered by two Class A/B Dayton Audio sub amps, each amp powering a pair in series).  I've recently purchased a JL Audio CR-1 crossover, which is a true swiss army knife for integrating satellites and subs.  I am considering using the settings on the CR-1 to control the subs and using Class D amplification for the subwoofers. I'm looking for recommendations and advice on questions such as:

1) Would it be better to wire two subs in series (effective impedance 4 ohms) and drive with a single Class D channel or using four separate Class D channels and powering each sub individually?

2) The passive subs themselves do not seem to be all that efficient. So how much power should I shoot for?  (Sorry, I don't have a spec)

3) Looking for suggestions on manufactured products.  I can envision anything from a four-channel design, two stereo amps.... OR if I keep the subs in series - a single stereo amp or two monoblocks.  I know that I can get a custom 4-channel amp from D-sonic (for instance) - but I'm not up on other reasonably priced options. 

4) Am I better off building my own?  It seems like hypex is as simple as buying the components and stuffing them in a case.  (But I'm pretty busy these days, so......)

BTW - I don't want to go wild spending $$$ on subwoofer amps!  Preferably I'd like to keep the expense b/t $1k and $3k.

Thanks in advance for helpful thoughts.