Buying another prusa i3

I will buy another 3D printer because I need a bit larger items to print and need heatbed 270x210
So I have few possibility.
First to buy ordinary 3D printer with 200x200 heatbed and modify it, change frame and heatbed to get 270x210.
[www.ebay.com]
Or to buy already 3D printer with heatbed 270x210
[www.ebay.com]
Or last one to buy a kit like this
[www.ebay.com]
and frame separatelly
[FwAAOSwnDxUjnqQ" target="_blank" rel="nofollow">www.ebay.com]

What do you suggest to buy to get good and working 3D printer for a lowest price?
That one with heatbed 270x210 have a metal frame, but this doesn't look really firmly and stable for me.

I have the one with the big bed and its frame is quite strong but... the bed is an issue with the 12v supply. Takes very long to heat for abs

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My printers:
-Makerbot TOM (#5215, circa 2011), MK6 extruder, ABS 3 mm
-HICTOP Prusa i3 (modded for auto-level, thread screws), ABS/PLA 1.75 mm

About me:
[www.thingiverse.com]

Did you have any other issues?
Heating bed takes alot of time for ABS with my printer too and it is 200x200.
I have changed bed for MK3 and it is alot better, withouth a glass!

Can some else share some experiences with me????

What material do you want to print?

The large bed machine above states it will only heat to 70C so you are limited to PLA. I believe this is a standard machine with longer travel Y rods, a bigger bed top and bigger shape heater. The larger heater is better for even heating evenly than just using the standard square heater with a longer bed surface.
I suspect that if you want to use ABS with a larger bed you will have to run the bed heater off a separate PSU as the control boards wont tolerate the current. There are suggestions on the web that this can be done by using a relay from the current bed connection to the new bed system. This means all the rest of the electronics are standard. But there's little point buying a kit with a heater you wont use.
Since it uses Ally extrusions for the frame of the machine it is easier to extend if you wanted to go larger. Why larger ? because you could have 2 standard bed heaters on a 440mm long bed. (One of my plans). I think there are kits out there that say they have a 400mm bed. I suspect that for a bed of over 270mm you will be looking to build your own which is a different discussion and there are other posts on here relevant to that.

For a bigger machine:- Standard electronics kit (without heater?) + PSU for bed + relay + bed heater (or 2), mechanical kit, your own frame parts and rods and carriage.

Hope this helps