In my experience, both machines (A8, what i have and A6) needs some upgrades, that can be easily done by the proper machine, and you can use the construction of these upgrades as a learning process.
Also, I have no doubt that for the most of the "diy" purposes is enough with any of them. With a simple knowledge you can achieve almost professional results.
Regards.
How much they charge to your country?
They are from Spain... they delivers for free if you buy more than 20€.
I also found some PETG spools on Amazon at good price, I have the Premium and it worths
There is no option on Cura to set it, I used Simplify and also Slic3r...
Dont worry about the heatbed, in theory, is not needed for PETG, so you can let it turned on.
Can you upload any pic about the results you are getting? Perhaps its not a temperature problem.
Regards.