Hey George, if you’re interested, I have a Z-Plus I took off my S3 XXL. It’s all in good working order. I’d let it go pretty cheap.
I did a fair amount of aluminum cutting with it and my DeWalt 611. Can’t compare to what you’re using now (assuming the belt drive z) since I didn’t have one. With the rails on tbe z-plus, it is more rigid than the belt drive, and better z-accuracy with the lead screw.
Don’t know what you’re making, but lots of examples in the forum of people doing fast/detailed and precise aluminum work on the S3 with pretty stock equipment. This is a good place to start with @Vince.Fab:
Now keep in mind, he was doing some pretty crazy stuff with the stock machine in the beginning, but towards the end I don’t know that you could call it a S3 anymore 
I’d also recommend you check out the mechanics of the machine. I was having a devil of a time getting good cuts, lots of noise, chatter, etc. with aluminum. Went through my machine piece by piece and discovered bad v-wheels, stretched belts, slipping drive pulleys, loose screws. It was a couple years of deferred maintenance on my part. And all of it I thought, well that’s so small, couldn’t be the problem. 
Each small problem compounded and made what looked like one big problem. So, if you’re experiencing a lot of chatter and noise, probably worth going through all the components, might quiet it down.