I'm starting a new thread on this because the old one has died out, but there has been extensive discussion of Tan Tan/Dan Dan noodles--see below. I'm no expert, but I liked the (not extremely spicy) Tan Tan Noodles at Siu Ga in the Lido Faire Shopping Center in Newark (just south of the 84/Decoto Rd. freeway to the Dumbarton Bridge). These were of the ground pork/ green onion/slightly soupy variety, were available as part of the weekend breakfast there. The crab dumplings, which seemed like an expanded dim sum item (though they didn't do dim sum) were very good too. The place was totally packed at 1:30 on Sunday, then rapidly emptied out.
Lido Faire is the "ethnic" shopping center in central Newark, surrounded by numerous whitebread models. There's also a pho place in Lido Faire that we like, though we haven't been there for awhile.