The Claridge is a good choice. There are of course many options in the US$ 80-100 range, but I think the names you mention are good examples.
Regarding restaurants, a quick list I can compile would be the following, (I apologize for not having time to post all the details including address, but you should have no problem asking your concierge for directions, all these places are well known).
1) Sucre (located on Sucre street, close to River Plate Stadium) - very nice place, also for people watching.
2) Cabaņa Las Lilas - located in the Puerto Madero area.
3) Oviedo - a traditional old-Buenos Aires style restaurant, with a serious kitchen.
For fine dining....
1) Nectarine - check with your concierge, the place is well known
2) Sinclair - go there for dinner, and make sure Ramiro (the Chef) is there...