Hi everybody, I am totally new to the CNC world and am hoping to lean on the vast knowledge of the users here to help me limit my initial mistakes and save some potential headaches. My goal is to prototype some small items I have designed which I plan on using the 6040 to create from foam and then casting them in 7075 or 6061 Aluminum. I am going to try to be thorough and explain my thought process and concerns and hope you guys are able to help me out.

My initial budget is around $1000-$1200 US for the base 4-axis 6040 CNC.
I understand there are potential issues with the base electronic components and would plan on upgrading them to ensure higher accuracy/speed and no lost steps, but I would like something that works to some degree out of the box to get familiar before I begin tearing things open and upgrading.
From my research the G540 is highly touted, as well as adding a smoothstepper. I would likely purchase a USB model 6040 to meet my out of the box needs, but believe I would want to go to ethernet controlled as part of my upgrades in the future.
I understand mach3 comes with many of these 6040s and have downloaded the trial and watched videos to familiarize myself with it, but have found a lot of other options such as UCCNC that people have spoken highly of.
I understand the 4th axis which comes with these 6040 is typically on the small/weak size but am hoping it would suffice for foam, at least initially so I could work on learning with it.
My designs are currently done in blender3d which has an option to export to .stl, but I would be open to learning a new CAD software if it were inexpensive and reduced headaches.
I have no experience with CAM software but would like one which was inexpensive but capable of doing what I need from it.

So my questions:

#1. Which 6040 should I buy? I have seen some reports that the tan painted machines and the unpainted ones may differ some? I am looking at a 1.5kw spindle version and would like the heavier model. I would also like at least the supported rail version as it seems the linear rail models are much spendier and out of my current budget. I am looking for as much rigidity as possible to start as accuracy is more important than speed for me.

#2. What is my best CAM/CAD/Controller route? As I said I would like something which will handle 4 axis work, which will be able to work with a USB (initially) and ethernet (eventually) inputs. I would like to do my designs in blender and export them to a CAM rather than learn a new CAD application, but would be open to learning one but not willing to paying many hundreds of dollars (or more) for a CAD app.

I am creating a 6 sided cube like object with 2 sides (top and bottom) requiring more accuracy than the other 4. My initial plan is to start with a foam cube and mill out the top side which has some holes bored in it. I would mill a rig from aluminum which had cylinders which matched the bored holes from the top side so I could flip the foam cube over to mill the bottom side. Then I wanted to make another rig which could be mounted into the 4 axis chuck to do the other 4 sides in one process. That could be done with 4 different runs each done after a 90 degree rotation or in one, I guess that doesnt matter as much to me. But I liked the idea of using the 4th axis for this more than having to re-position each side manually. Once the foam is milled I will cast it and would then like to use the 6040 again for cleanup/finishing on the aluminum.

I have tried to read all I could here and have learned a lot, so I appreciate all the information put out here and apologize if my questions have been answered many times over (probably have). But trying to navigate through all the threads and pull out the valid bits was a bit overwhelming so I decided to specifically talk about my needs. Hopefully I have provided a clear enough view of what I am trying to accomplish that you can give helpful input! I am very open to whatever questions you may have as you guys likely have questions I dont even know to ask yet. Thanks for taking the time to read, any help is greatly appreciated! I am planning on making my purchase in about 3 weeks so I will continue digging until then.