Keeping in mind that you are going from an Atlas 618 to whatever you choose, anything larger is going to be an upgrade, to some degree. In general, for anyone upgrading in size, the majority of the cost is in the tooling. This is often overlooked. Myself, I have had many lathes, but mostly buying an selling until I had what I wanted. After a few, I met my first love...my forever lathe was my Emco V10P. I collected every bit of tooling applicable - it had a 1.5"/8tpi threaded spindle. Eventually I had every chuck I could want, Faceplate, steady rest, follow rest, DRO, AXA QCTP with a pile of holders, 3/8" and 1/2" shank holders, change gears for every thread, and so on...tons of $$ invested. It was a great lathe, but it wasn't super rigid. I could take a 0.0400 cut on mild steel before HP limited it, but it was very precise. I grew to hate the threaded spindle, after an incident...I think i posted about on here, and it was a bit small, and I wanted a 3 phase machine with a VFD.... I wanted its big sister, the Emco V13, and after years of searching, I finally found one. I sold the V10, and started over retooling the V13. I have spent thousands, even though I kept several chucks from my V10p, but its my for sure forever lathe. I bought new backplates to fit the D1-4 nose, new BXA qctp tool holders...got if fully tooled up, Brand new Ditron 3 axis DRO, etc. Spent thousands.....Then I found a very nice Monarch 10ee. The Holy Grail.....and it has a D1-3 spindle nose and now I have to start all over....If i keep it.
Moral of the story, since you are buying new, is to decide carefully. You have a lot of choices. It can be very costly to tool up a machine and then decide that its not quite what you want. The tooling is the expensive part, and it will change with the machine. Nevermind the hours of research/learning on a particular machine. You are way better off spending more up front to get the machine you will truly be happy with.
Also, In my opinion, I would not want to buy a NEW lathe if it didn't have a D1-x spindle, clutched feed shaft, and the option for a 3 phase motor, so I could install a VFD. That all can be had for not a lot more money, but it separates the toys from the real machines. Also, you have to think of resale value. There is no doubt that PM machines have a much higher resale value than Craftex, etc.
Just some rambling thoughts on the subject