When choosing a Longarm with computer, one needs to thoroughly investigate both before purchasing. Additionally, what works for one, might not work for another.
Quilt shows are a good place to try many different brands. However, most computer system upgrades start at $10K, which would limit your machine and table combo to $10K to stay within your budget. Handi Quilter has an 18” option with Computer that would keep you within your budget, if you must go new.
If it were me, I’d look for a used Gammill Statler. The software is a free download (but can’t be used to stitch out) from Gammill’s website, as is the manual. You can download both to your Windows based computer and work your way thru the manual to learn how to use it while waiting for a used one within your budget. I ordered mine new, downloaded the manual and software while I waited for the machine to arrive (two months) and by the time it arrived, basically only had to apply the knowledge gleaned from my study and research. It’s extremely intuitive and both the machine and table are solidly built,