Cheers

Tom

that is not to say you can't do ABS on an open frame, you can, just that it is more challenging.
ABS likes a warm environment, and does not like any kind of drafts.

I'm looking to get or build a printer with a larger print area, like around 8" cube.

Should not be hard to find that is more or less a common standard size bed these days.
a caveat remember this is 3d printing so doubling the size is really 8 times the size. for example a if a 2 in cube takes an hour to print a 4" cube will take  8 hours to print and an 8 inch cube will take  64 hours to print. Also the material use will be proportional to the time as well so material use is exponential as well.
That said I have seen a couple of huge prints done on a g max and I am looking to buy a printer with a 12" x 12 x 15 build area.

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Electronics: cheap controller $50  genuine quality $150. Real driver chip $ 8.00 cheap clone $1.50 . ED3 knockoff $14 genuine ED3v6 $73  cheap motor $10-$15 ea name brand quality stepper $50-$80 each. This is why a ultimaker has a price tag of $2500 -$3500 so quality has a higher price tag. The question  is real cost real parts are going to have a higher reliability .

so do you gamble on cheap or invest in quality. 

higher purchase price. So when people are selling printers or kits for $250 -$500 there are going to be compromises .

So what to look for
Metal frame
quality components
real lead screws
layer fan if you like PLA
heated bed
on board control
build area size
Boden extuders print faster but can be problematic for flexible material
all metal hot end  extruder temp range materials that can be printed
cheap hot ends have limited temp and will not print higher temp materials like nylon
ABS you pretty much need an enclosure  to keep higher even ambient temps.
you can build an enclosure or use a cardboard box .
PETG is becoming more popular and does not warp like abs.
The wanhao duplicator  is a pretty good value pussa clone.
The robo is probably a good option but again without an enclosure not an abs machine.

Where in the world are you . IMHO the best option is to visit an independent 3d printing store that has 10 plus makes and models in there show room or visit join a local maker space that has multiple 3d printers so you can see and use different ones.  Yes these places exist.

I do have an opportunity to buy a Robo r1 plus for 450bucks, used. It has a nice build area, like 10 , 9, 8 I think.