I agree with hydrochron...Vyvanse does turn into dextroamphetamine (Dexedrine) once its inside you but it does have a lot more side effects compared to straight dextroamphetamine. It's not secret that amphetamines and opiates combine well, I have lots of experience with this combo, but, sadly, no experience with amphetamines and buprenorphine as a combination.
I would take hydrochron's word, though, since I've heard from many sources that buprenorphine is quite speedy and clear headed just by itself.
Buprenorphine + benzos, on the other hand...a good plan.