I have owned around 9 printers now.. The rostock max v2 was my first ever printer.
My thoughts on it.
The build volume is NOT as big as it could be, because its a delta, meaning its a circular build plate, so you have to square off the circular area to get the build area (unless you print 100 tiny parts that fit in to those circular corners). It can print call, but X and Y not a ton.

Now I preface this by saying this was my FIRST 3d printer, and i learned a lot by building it, but i didnt feel like the print quality was good enough. Howevver, after owning many more over time, i put it on par with a prusa or rep rap printer. No where near my FlashForce Creator pro for quality. but on par with the others.
Leveling the bed was a nightmare. way harder than a square bed... Maybe there is ABL on it now. which would be great.
i dont want to sound down on the rostock max because I think its super cool, i just think for you wanting bigger than you have now, you need to look at something bigger.

You can build a gcreate xt1.5+ 16x16x21. I have one coming tomorrow (fully built) but you can DL the files and build it yourself.