I bought my Z2 from cartronixplus.com as well. I'll describe the situation and you can come to your own conclusions.
I went to the website to order the unit. I couldn't find any information on whether or not the harness was included for my vehicle. Then the internet account registration crashed in my browser.
Undaunted, I called their number. They took my CC info. According to the rep, I was getting the last in-stock unit. I told them about my account creation issues, and they said they would fix it. Okay.
Wait two days, no shipping info. Check the website, my account is still borked. So I called. Several times. Finally, they called me back. Turns out my unit had indeed shipped, but was "destroyed in transit" with UPS.
Ooooookay. When will I get the new unit? They tell me a new shipment is coming in the next day. I tell them my account is still borked. They say that they'll take care of it. I wait.
Nothing.
I call again. Finally get an answer - shipment delayed. Okay. I wait some more. No dice. I call YET AGAIN. Shipment still delayed.
I wait MORE. At last, I call them, determined to get my $$$ back and cancel the order. They say they sent me tracking info the prior day (to the wrong e-mail address). Finally got the unit and installed it.
Was any of this drama their fault? If you believe them, no. If you're a skeptic like me, however, it is difficult to believe that they're victims of circumstance that many times in a row.
They: 1) never repaired my account - I still can't login, 2) told me I would get the unit by a certain time, which I did not, and 3) still have not corrected my e-mail address in their system after much prodding.
All that said, I got the system, brand new in box, and it works flawlessly. Next time, I'll pay a tad more and buy a little less drama.