the domain helps but it's not the whole story, your <title> and <h1> have a HUGE impact on where you index. if your first site is pr1+ i would build on it rather than start another pr0 and work up. think about it, stanleysteemer owns the term carpet cleaning. the words carpet cleaning are no where in their domain.
301s will push traffic but they will also get the site with a 301 to fall right out of the ranking since the site isn't what it was.
you can do this a couple of ways, i'm just not sure i would give up an aged ranked domain for a brand new one when it's such a similar line of work.