I think the answer to this question depends on your preference for variety as opposed to quality. There are many good vendors for many kinds of teas, but in general, you have to trade selection and price for quality when looking at a single vendor. Here are a few good vendors at various points in this spectrum (listed from more variety/low quality/low price to high quality/less variety/high price):
- Rishi tea
- Dragon Tea House
- Yunnan Sourcing
- NadaCha / Essence of Tea
- Best Tea House
Ippodo is the only Japanese vendor on this list, but based on my experience, I have yet to find a vendor of Japanese teas that beats Ippodo on price, quality, or selection.
I would probably choose one of the vendors listed here. At the moment I have been drinking a lot of Japanese teas, so I would probably choose Ippodo.
There are many vendors, especially boutique or "indie" vendors, that I have tried recently that have treated me well, but they are mostly too narrowly-focused and I would get bored of having the same kind of tea over and over again.