Zinergy has a point.
It is well known that both amph and methylphenidate can cause growth suppression in children treated for ADHD. This is most likely due to appetite suppression coupled with increased activity.
As for metabolic effects, yes they will increase lipolysis (like ephedrine), especially if combined with excersize, but they also cause increased lactic acid buildup. (This can be prevented by adding insulin in low amounts)
Amph will also drain you in terms of dopamine release, but this might be rectified with proper nutrition and using only low doses of amph.
I've tried methylphenidate as a pre workout stim, and it's not so bad, but it has a shorter duration than amph.
I think you can diet down on an ACA stack, but the effects on sleep and appetite (and eventually fatigue) will be worse than with ephedrine. Ephedrine has very little effect on dopamine release, but is more powerful than amph when it comes to beta stimulation. It doesn't drain you in the same way.
Dexamph will be even more of a pure dopamine releasing agent than if using racemic amph (both the dex and levo isomer), and I'm not sure how it will effect you.
You could ofcourse try it for a week and give us an update, then try a week of regular ECA and see how they compare. I'll suspect you'll get better sleep and nutrition on ECA, as well as more strength in the gym over time. But I could be wrong.