Okay, I have the answer (if my calculations are correct), if anyone wants to know.
First, I looked on the web and found out that 10mg of Adderall contains, when the other components of the salts are removed, 6.3mg of amphetamine (there was a nice chart on some site).
Then, since that’s ‘amphetamine’ base it includes the l-amp, so we have to multiply by 0.75 to get the amount of dextroamphetamine base, which means that 10mg of Adderall contains roughly 4.73mg of d-amp.
Next, since I couldn’t find the equivalent of amphetamine base for Dexedrine, I decided to try to figure it out for myself. I looked up the molecular weights of amphetamine and sulfuric acid and found them to be 135.21 and 98.07. But there’s two amp molecules attached to the sulfate, making the total molecular weight 368.49. Taking a percentage (73.4) we find that the total dextroamphetamine in 10mg of Dexedrine is roughly 7.34mg.
So, if we’re ignoring l-amp we have 1mg Dexedrine=1.55mg Adderall (which if we round to 1:1.5 it makes conversions nice and easy).
So my 25mg Adderall is equal to roughly 16.13mg Dexedrine. So it should be just slightly stronger than the 15mg Dexedrines I was taking before, plus anything that the l-amp gives to it.
And I did all this on Adderall--instead of saying 'eh, whatever.' I think the Adderall is, in fact, working quite nicely (although I kinda miss the greater speediness of the Dexedrine, even though it’s probably better that I don’t have it). One drawback is that it's a good bit more expensive than Dexedrine, and my health plan with school only covers 80% of prescription drug costs, so I have to fork over the other 20% for this and the other drugs I'm taking.