Geoff,
I actually like your first rendition, the stars are small, the nebula sits out, in the second one I think you have baked it a wee bit to hard, where the stars are now bloated and have lost colour.
A happy medium between them sometimes is a good thing.
My work flow to add in Ha to a image is kind of the same as Greg,
I have pasted a synthetic luminance procedure on my site, though its virtually the same for adding real Ha. where i take the red channel out of the main image and past it into a black and white blank canvas. put a nigh on over processed Ha ontop and set it to luminance, adjust opacity so its not garish but brings your details though nicely.then past it back into your red channel. i go into depth in my guide.
Often you are looking for subtle effects where it sharpens up a certain Ha detail and gives a overall effect. Remember you want to draw attention to areas you want people to see, Try and only have a few of these areas so that your eye doesn't become distracted, too many just over complicates the end image.
http://brendanmitchell.net/?page_id=213
just click on the tutorial and it will take you though the steps
Brendan