A question I have pondered myself over and over. From what I have seen the delta design is quite scalable. You can gain some z by shortening the arms or gain some xy by making them longer. The trade off is if you make the z large the xy gets smaller and visa versa. in reality if you want a bigger envelope you need longer frame parts and longer arms and longer belts. and in some cases longer linear slides.
IMHO if you get the 2020 and use 1 meter pieces for the verticals and 500mm pcs for the sides you will get a nice size print area I have not done the math.
I will say that kit is tempting.
looking at the specs i see a couple major shortcomings. Power supply is too small . No heat bed. Ships direct from china soo take your chances on customer support. hot and max 280 should do most materials.
A common problem with these kits in general is the plastic connectors are generally of low quality. Not uncommon for folks who buy these kits to have to print there own . A problem if this is your first printer.
I think if I did a kossel I would spend the extra $ 100 and source aluminum corners effector and carriages.
Take a look at this one. Ships from USA , aluminum corner connectors ,heat bed included, 300 watt power supply only downside is LCD controler is a $12 add on.
http://folgertech.com/products/folger-t … rinter-kit
I suggest you download the build instructions and read them before you buy any kit.
Happy Shopping
Tin
Soliddoodle 4 stock w glass bed------Folger Tech Prusa 2020 upgraded to and titan /aero extruder mirror bed
FT5 with titan/ E3D Aero------MP mini select w glass bed
MP Utimate maker pro-W bondtech extruder
Marlin/Repetier Host/ Slic3r and Cura