Domt be apologetic about getting excited over grasses. They are exciting plants amd very much undervalued
You can buy plants now but don't plant them out until spring. I have some local nurseries but Hoecroft nursery is very good. I initially bought all my grasses from them as very small ones. Often the roots are bit congested as grasses, ESP the bigger ones, are vigorous. I simply untangle the roots and pot into a bigger size.
Miscanthus, Calamagrostis, stipa gigantea, and panicums are excellent tall grasses and there are new varieties added all the tme. Deschampsia is a great choice for a dampish spot or one with good soil growing about 100 cm amd flowerimg over the summer. Check it out
Enjoy your grasses Forester.