I am going to give it a try. I ordered the Now brand of Rhodiola and it is a 500 mg capsule also with 3% rosavins and 1% salidroside and over 400 reviews from iHerb.
You may l find that 500 mg is too much, these herbs not only have very different effects on different people (with a meal, without meal too, different brands=different results), but dosage can also change the experience in a very important way. More is not necessarily better, smaller quantities in each caps allow for fine tuning .
The brand I use is also 3% 1%, the origin of the plant may be important too (different soil and climate often mean different composition of the herb).