IMO the only good maxxisonics boards with hifonics are the xx and xxv series (same boards as other proven bigboy amps)...anything else is mid level or lower. The maxxisoncs employee even chimmed in and said the ZRX line is entry level and not RMS rated...
I've been using an ap3000.1d for the last few months with only one side hooked up to my 1 ohm load and it's been remarkably impressive for only a rated 1500w per side. I'm sure both sides hooked up with enough juice behind it and it'll be beast out.
Steve at ampmedics (who lives and breaths 3kw and up amps every day) says the ap3000.1, powerbass 3k, and crescendo's are some of the best amps for the money. He laughs at the fact the crescendo 5500 is the same board as the saz-4500d and costs signifigantly less.
That all being said I just picked up a 1ohm stable amp for my setup and I'll be listing for sale my ap3000.1 this week. Shoot me a PM if you need 2 ohm power. We can work out a decent price for mine. It's in good condition and you wont be paying almost $400 for an ebay one