I have a concern about those lights.
They appear to be a no-name brand, and most likely made in China. The odds are rather good that China stole them from someone they were making them for anyways(as in: thanks for all the information, we'll go make our own now). I question quality and support because when left on their own to do things, the Chinese will use parts that while are up to spec, are not the same quality of the parts the company hiring the work would have used. The Chinese will typically use LOWER quality parts to drive the price further down.
Trust me, I got insight like mad into the Asian mindset.
Chances are, these are actually something else re-branded and using lower quality parts. I'm not trying to PUSH the ADJ product line. I do know that most ADJ fixtures are in fact made in China, and honestly, so is most of what everyone else has too. But when the Chinese steal from their non-Chinese employers(how do you think the Chinese got their space program? They stole stuff from the United States, that's how), they tend to do what they can to destroy prices and undercut to make sales.
Let's look at some other stuff. ADJ makes the Mega Panel. Chauvet makes a essentially the same product, but at a street price of about $80 less. Now, for my purposes, the Chauvet fixture does what I need it to do. But, looking at the DMX traits, I can see that Chauvet is able to offer a lower price by having fewer features, so the DMX chipset isn't as expensive and that's where the cost difference comes in. So, in those regards, I'm glad I stuck with ADJ products mainly so I have more options available, although honestly, I'm probably never going to use them.
Comparing the ADJ LED cans to the Guitar Center brand of "Venue" lighting offerings, I see a lower price on nearly identical fixtures. Well, there has to be a difference in price for a reason. That's all I'm going to say.
I'm not going to sit here and say "buy ADJ", because sometimes ADJ just doesn't have what you're looking for, and that's fine. My warning comes from experience. Buying a QUALITY fixture cheap is a great deal. Buying CHEAP fixtures may appear to be a great deal, but in the end, when you gotta replace them, how good a deal was it then? My thoughts to you, Mick, are that I hope that regardless of what you bought and what you spent, it lasts you a GOOD long time.
And let me also say this:
You're gonna LOVE the 3D Visualizer in MyDMX. You can really design your whole show without needing to plug in a single light. While perfection isn't possible, you can get really really close. Like, in my case, I can't do mover points exact until I get to the venue, but I can get close in my design and fix it at the event. You'll be able to see your washes and your transitions and see if you like it or not, and if not, tweak it until you do or trash that scene and start over if you want to.
Since you're talking wash only lights, don't get fixated on being limited to washes. MyDMX has this cool FX generator that you can do patterns with your lights. Think a rainbow movement, or maybe marching, or on/off patterns, sine wave stuff, a "knight rider" type thing. You've got a fantastic tool box full of wonderful toys in there to play with, and you just get more things to play with when you add more different lights into your inventory.