I would second doing foster care first...seeing how things work with your family. We have 3 adopted children, they were 2, 3 and 4 when we brought them home and we've had them for a year now. We also have 2 older bio children, who were in on the decision to adopt, and very positive, even when we mentioned all the 'what ifs'.
The 2 year old showed some signs of trauma, as did the 4 year old....sadly the 3 year old has been the straw that broke the camels back since he came home

He has attachment issues, and he's very superficial towards us (until you're out in public) and then he's downright mean......saying things that aren't true but when others hear the things he says you can just see their eyes light up. It's sad....all they've been through, all the moves they've made....they didn't know any other way to act. He says mean things because he doesn't want anyone to love him and he doesn't want to love anyone else, that way when he gets moved he won't be hurt as bad. Sadly it'll take years for him to ever understand that he's not being moved again....and he might never heal from those first few years of trauma, where that attachment bond was broken so early in life
While we all want adoption to be a positive experience, and the kids to love us and us to love them...it doesn't always work out like that. Sometimes we're meant to be a stable home, with love and room to grow until they are old enough to leave the nest.....and they may never feel close to us like a bio child would. I pray that our situation grows more positive over the years to come, but we've given up our preconceived notions of what we wanted our family to be and opened our hearts and minds to what it IS!
I would also suggest reading up on all the RAD books you can get, we were told that our children did not have attachment issues....but came to find out that a HUGE percentage of children in the system have attachment issues....even if they are just minor ones. Our children all went through that period of 'anger' where they broke everything we gave them, lied uncontrollably, crazy lies...etc And then as I said before...our middle one just keeps on going through all sorts of stages. So prepare for the worst and maybe you'll be pleasantly surprised when things don't go that badly
Some of the books that really opened my eyes were:
*Beyond Consequences, Logic and Control (this one helped me understand that just because I raised to healthy, well adjusted children my parenting skills would NOT work on these children the same way. I've had to readjust everything I do...from discipline to scheduling...etc.)
*When Love Is Not Enough (this one is written by a mom that has successfully raised RAD children, even ones that have killed...etc. Again....you'd be amazed what even some toddlers can do because of the broken link in attachment from birth mom and dad

it truly is a tragedy...and then to be moved over and over because people didn't really research what they were getting in to, just compounds the issues they are already dealing with).
I'm not trying to scare you, and truly...these kids are a blessing to us and I love them more and more everyday. But it definitely wasn't what we expected, and most attachment issues won't show up until after the 'honeymoon' period....which is after you've finalized the adoption in most cases. Again, just go in to it with all the research in your mind....and be prepared with counselors that are educated in ADOPTION issues...not just kids in general. Good luck!!! Oh and a small note....if you adopted 1 it's probably way way easier LOL Adopting 3 was hard, we wouldn't change it, but still it was really really hard on all of us.