I'm sure every pregnant woman is different on what she can tolerate while pregnant. Scientific studies and doctor recommendations seem to change all the time.
When I was pregnant with my daughter, I quit drinking anything with caffeine in it (and I was a major Mt Dew drinker). That was my decision, though. Ate veges, fruit. Gave up a lot of processed foods. Didn't eat as much meat. Drank a lot of water. Basically, adopted a better eating habit (I wish I had kept that up; when my daughter turned 7 I had to adopt a better eating habit because of health issues/food intolerances and allergies. It was HARD to go back to eating organic/well when I'd gotten used to eating all the bad/junk food again!)
For me--and a lot of moms I know--your body will let you know if it doesn't like something. That's why there's morning sickness. If drinking caffeine--as long as you don't drink a lot of it--doesn't make you feel sick, I don't see any reason why you can't have a small amount of coffee/caffeine every day.
I drink tea and would absolutely hate giving up my tea! I drink green, black, herbal. Granted, tea has about half the amount of caffeine coffee does--so I get 2 cups of tea for about every 1 cup of coffee for about the same amount of caffeine--and I can't drink a lot of tea because otherwise I can't sleep at night. But not being able to have any caffeine would be unbearable.
You want to eat better and healthier but you don't want to deprive yourself either. Unless the caffeine from the coffee is upsetting your body or keeping you up at night or causing your baby to be super stimulated (lots of moving around) I would think 6 oz/caffeine/day should be just fine.