I'm sure we've all got some great favorite nurseries/greenhouses in our region. My favorite is a well-kept secret: LURGAN'S, near Orrstown, PA. It's a family run business and it is OFF the 'net so you won't find any website and you can't place online orders. But it is worth the trip. The place is huge (they recently added another gigantic greenhouse), and the selection is astounding. They have a truly wonderful selection of water garden plants and materials; the display of fountains, waterfalls, containers, etc. in the front is amazing. Prices are good, the quality is very good. Plus, depending on when you arrive, you can sometimes get small "starter" plants (rooted cuttings) at very low prices ($2/pot). There is not what I would call a "knowledgeable staff" on hand, so I usually go there with a copy of any good mail-order catalog I have on hand so I can look up plants and get info.
If you go, expect to spend at least 2-3 hours browsing the place.
This place is well hidden. It's back a narrow (but paved) winding rural road. Once you find PA Rte 997, however, you're in like Flint.