You are will want to transplant the seed to a soil mix close to your garden soil...
Reamber wisteria from seed will take about 5 years to flower...

Do you intend to grow these in pots long-term, or are they intended to go in the ground at some point?

I fail to see any reason why you cannot grow them in the gritty mix. I would water more often, not look for more retentive mix, which would negate the reason for using the gritty mix. Use a weak fertilizer such as half a teaspoon per gallon of Foliage Pro every time you water. In gritty mix it is easy to underwater, but almost impossible to over water. Al

Thanks all for the comments. Here is a quick update.

I am planning to grow these as bonsai. I started from seeds and now have one each Wisteria Sinensis and W. Sinensis Alba growing. I know it will be years before they bloom, but think how exciting that day will be!

So - I have added a saucer under both to create some perched water. I read this suggestion at a bonsai forum and thought I would try it. It seems to be working, both seedlings are now growing well again. From what I have read they do not like to have dry feet, so this approach seemed to work best for me. I want to keep most of my bonsai in the basic 1-1-1 gritty mix as it works very well for my others. The only exceptions are my 3 giant sequoia trees. I planted them in the 1-1-1 mix with 15% peat moss by volume and no lime - they are growing exceptionally well.

As for the foliage pro, I shoot for 50 ppm nitrogen - 1/2 teaspoon per gallon is about 59 ppm and seems to be working well.