Oyster House: Based on faint memories of childhood visits to family friends in Philly (think Old Original Bookbinder's), I couldn't leave town without some snapper soup. The Oyster House version did not disappoint. Nor did the clam roll, featuring large chunks of clam in a light and crispy breading. Perhaps strangely (but this was lunch the day after our Estia fish dinner), the other of us opted for the Oyster House burger. This turned out to be a first-class Angus beef burger topped with caramelized cippollini onions, blue cheese, and (wait for it) a single fried oyster. Delicious. And the ambiance was perfect.
Unfortunately, here again a (relatively minor) service problem: After finishing our sandwiches, we ordered hot tea. Ten minutes later, still no tea. The server apologetically explained that "the water wasn't very hot" so he had held off, waiting for the water temperature to rise. As time was running out for us, we gave up on the tea, paid our bill, and left.
Sbraga: Bustling ambiance, but not overly noisy (unlike Osteria), and excellent, imaginative cooking. It did seem that no dish was deemed complete without an Asian-fusion element. And every dish we ordered was pretty rich, although not to the point we couldn't handle it. Service was excellent, although we did think that 5 separate people (including the busser) asking us if everything was OK was a bit much.
The 4-course prix fixe menu was fairly priced at $49. But we would have preferred having a 3-course option to consider. The portions weren't enormous, but neither were they so small that 3 courses wouldn't have sufficed, especially before a Kimmel Center concert and given the richness of just about everything on the menu.
The wine selection, in contrast, did strike us as pretty pricey. Many interesting bottles, but not only no bargains, many in fact seemed extravagantly priced for what they were. Trying to settle on one bottle to cover a variety of dishes, the server suggested a grignolino d'Asti, which filled the bill appropriately but was priced at $87. For a grignolino? Hard to justify, we respectfully suggest.
All told, we ate very well indeed during our three-day stay, and hope to plan another visit before too long. Thanks again to all on this board whose observations and comments on various threads were so helpful as we made our venue choices. We hope these observations of ours will be as useful to future visitors, if not to Philadelphians themselves.