reason why/why not to have more kids

It wasn't until just this morning that the last bit of little baby Kylie wore off and has been replace with big girl Kylie.  She just feel so big...not at all like the little helpless munchkin that I used to rock to sleep every night.  She sad realization is she is just going to keep on growing and growing and our days of baby Kylie are as good as over.
It also was not until very recently that I doubted my plans to give Kylie a sibling.  While, that has always been the plan (what better gift can you give a kid, than a life long playmate??) I wonder if my heart can swell any more to make room for the next possible member of this family.  As an oldest, my parents, obviously thought they had room for another one and I do not recall feeling slighted or replaced when she arrived, and they must have been sure that they had enough love to give another kid, even if it was purely to give me a playmate so I'd leave them alone.   I just think she is so great what are the chances we will be able to recreate that again?  I'm telling ya, she blows my mind.  How did I ever deserve her...and more so, how do I deserve more than her?
But then...if I don't...I'll never know what could have been.  Would we get our boy? Would the next one actually look like me? Would we be able to successfully financially support a family of 4?  As I pack away all of the adorable little clothes and reminisce about all the whirlwind moments of the last year and a half I start to crave it all again.  The newness, the smells, the closeness, the sleeplessness, the routine. 
The greatest reason why and why not to have another one is sleeping in the room next to mine right now.