Help me understand how to optimize bass on the Zu Definition Mk IV

I am a longtime owner of Zu Definition Mk1.5 speakers and recently also bought a pair of Definition Mk4's. I based this decision partly on the reviews / feedback posted here on Audiogon in various threads by members such as 213cobra, gsm18439, spiritofmusic and others. I'm really hoping some of you Mk4 owners can chime in and help me out here!

Basically, my issue is that I found the Mk1.5's put out incredibly deep and impactful bass, especially with some of the music I love, like R&B and reggae. And this was with the bass amplitude knob at 12 or 1 o'clock. However, after setting up my new Mk4's, I find the bass underwhelming and anemic, even after fiddling around with various settings and with the volume and PEQ cranked. I have them on spikes into bases on a hardwood floor, with about a 1.5" gap on the bottom. What am I missing here?? Based on the reviews I read, I was expected the bass to equal or exceed the lowly 1.5's. 

Thanks so much in advance for any helpful advice! 

Yes, you should solve grounding problems. You're hearing hum through the Radian compression tweet? That's strange. No, the Zu Def power cables aren't introducing ground loop hum. But you probably have induced some ground loops in your system connections, and it's likely your ground points are not all on the same plane. Solutions are always elusive. If the sub amps' power is contributing, it's not the cords, it's having them plugged into a different circuit. By chance, do you have cable TV among the sound sources into your system?

Also, is any portion of your system balanced or running balanced or XLR cables? Mixing Bal with SE can also surface ground problems. What is your analog chain (phono-pre > pre) and is there an SUT in the mix? How many (if any) of your components have ground-lift switches? Do you have any passive components that are not separately grounded? What's your phono cartridge and tonearm, and how closely are they placed to anything else with a substantial power supply?

Just some questions for which answers may narrow your suspects.

David, Phil is right. Do not expensively spend on subs ancilliaries until you've got basic setup right. At that point if you're happy, and want to go on, my personal experience is that choice of pwr cords and fuse makes a difference.

I'm stuck with a little hum in my Zu sub amps that I'm still searching for a solution.
Yeah, I'm not too interested in spending much on power cords etc. at this point. I was just interested in the grounding posts you had installed on the Zu's and your overall power management scheme, as I've struggled with some hum and slight buzz in my system. I do have the subs on the speakers on a different circuit, which I realize is an issue, but was more practical given how things are arranged in my listening room. Also, I misspoke when I said the ground loop hums are coming out the tweeter... obviously they are oscillating at 60hz. I actually only have a small amount of 60hz hum present in the FRDs and not audible in the sweet spot. I do, however, have some hiss and buzz out of the tweeter when the phono is selected on my turntable. I was able to reduce the buzz significantly by running a ground wire from the lamp above my turntable (on a dimmer, which is a likely source of the problem) to the turntable itself and then to the preamp. I had considered a star grounding scheme for the whole rig, which worked wonderfully to lower the overall noise floor when I did this for the analog mixing setup in my home recording studio. In such a configuration with grounding posts on the speakers, I could then lift the grounds on all but one of the components for a single path.
Request ground posts for Sean when he looks at yr amp modules.

I'm sure you'll like the Gaias footers, some mileage there.

The other thing to say David is that eight 10" woofers versus two 12" was always going to present a difference, esp rear facing versus down firing.

I think you need to approach the 4 as a different spkr to the 1.5, blank canvas approach on set up.
Very true, Marc, I'll start from square one with setup once the amps are back. I really appreciate all the help you and Phil have given me here. David