I just wanted to say that I too, have felt this way, especially in the beginning of the pregnancy. It scared me when I realized a part of me viewed the new pregnancy as a kind of "second chance" to finally bring her home.
As time has gone on, it has helped me to notice the ways in which this child is very different from Ila (eg., sleep/wakefulness patterns, activity level, the fact that she sucks her thumb in all the ultrasounds, my own reaction to/craving for certain foods, etc). They are subtle things of course, but they have helped me tremendously. In fact, the differences in this pregnancy overall were enough to make both DH and I convinced this one was a boy (which it's not!).
I can completely relate to you saying that as you prepare for your little boy, you want to remember Amelia as well -- I find myself doing the exact same thing. I think your baby blankets idea is just wonderful. In fact, my best friend had been working on a little flannel cuddle blanket for Ila when she died. She sent it to me a couple of weeks later, thinking it was something I should have anyway. She had embroidered her name on it. It may sound a bit odd, but I sleep with it every night, and somehow it brings me a small bit of comfort.
Wishing you all the best.
angel Ila Elizabeth (02.06.04), 25w2d ~ severe pe/Class 1 HELLP
pea-in-the-pod, EDD 03.04.05 (37 weeks)