Well, how old are your boys now? And how old would they be when you're thinking you'd have a third? Are you a SAHM? Is your dh supportive and helpful with household/parenting stuff?
We always said "two, maybe three". We have three. I was one of three, and two just didn't seem "done". I somehow felt disloyal to my brother (the third kid in my family) - like he was optional. He NEVER would have thought of that but I did and couldn't bear it. I can't imagine childhood or adulthood without both of my siblings.
The chaos - yes, there is definitely more chaos! Not right at first, when the baby is still a baby (I thought it was a cake walk then). But now that my dd3 is three - whoa! Chaos! It actually started as soon as she could walk and talk - really be in the mix if you kwim.
It is not that much more difficult to manage in that you already know what you are doing, and how to split your focus (the hard part of going from one to two - I found that one to two transition to be the hardest). It is just more splitting, more chaos, more kids to argue with (instead of just the one - with each other as siblings, not me!)
I drive an SUV so the carseats all fit - we have three rows! It actually is nice to be able to split them up and not have them all right next to each other. Baby went through a phase where she'd kick, kick, kick her feet in the car seat and gave dd2 a few bruises doing so. You just couldn't get away from her feet with the carseats right next to each other. If you have three kids, just give in and get a minivan or SUV. You really will need it. Think carpool and bikes and soccer gear and....
My dh drives a small truck. The two carseats and one booster would fit in the back if you were really good. But it involved a lot of bruised knuckles and some cussing to get them in there... (the carseats in there, not the kids...

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Yes, there is quality time with each child. Just not very often... We try but it is usually maybe once or twice a month. If you space it right, you can have some one-on-one time with the third when ds1 and ds2 are at school/preschool. I can see where this will (hopefully!) get easier when the third is a bit older.
Alone time - this is absolutely ESSENTIAL if you are to remain sane!!! I needed it before (with two kids) but now I go right over the edge if I don't get enough. You MUST put this as a priority. It cannot be at the bottom of the list.
I am 37 now. Dd1 will be 10 next month. Dd2 will be 6 end of the summer. Dd3 just turned 3. Honestly I am a bit tired of diapers and sippy cups and not being able to walk through a parking lot without holding a hand. Dd1 and dd2 are such "easy" ages now. We can take them anywhere. Dd3 is a spitfire and really the most challenging of my kids. We can't do anything unless we leave her home with a sitter - or either my dh or I sit with her outside of whatever event it is. The older two had such great attention spans and ability to sit quietly (for restaurants or concerts or sister's piano recital, etc.) Dd3 cannot do that at all. I think in another two years, my life will be infinitely easier!

Just the other day, I found out a friend of mine - who grew up as one of two kids - had her brother pass away. My dh had a brother - who passed away when my dh was just a little kid (he essentially grew up an only). I know it is a weird and morbid thought - but I am happy that my girls are one of three.
So anyway, if you'd have asked me when dds were 6, 2 and newborn, I'd have said it was easy. If you asked me today (9, 5 and 3), I'd say it was HARD. I think (hope....) that if you asked me in another two years, I'll be back to a "really doable" type answer.