Well, I know this query was posted a long time ago, but we actually stayed in Hostel Astoria in Barcelona recently. It was about a 5-7 minute walk to the Diagonal Metro stop and just beyond that stop (about another 5 minute walk) is the Casa Mila.
The hotel was really nice: the lobby was very pretty, and the rooms had been renovated recently so they were quite modern and spacious. We ate our breakfasts and dinners there and they were some of the tastiest meals we had on our tour of Europe. The staff was very friendly and spoke English, although I'm not certain to what extent they knew English since I usually spoke to them in Spanish. We departed the hotel on New Year's Eve Day, and the staff brought our room small bags of grapes for the campanadas as well as a red rose.
Before you think I'm working for the hotel or something like that, I could tell you that our cable wasn't properly plugged in, although we never bothered to tell the front desk since we were hardly in the room anyway. Also, the bathtub could have used a little drain cleaner, but again, we never told the front desk of the problem.
The neighborhood is more residential, but there were plenty of small neighborhood shops (albeit many were upscale clothing stores), bars, and even a grocery store nearby. It was refreshing not to be in the middle of a tourist area, actually.
So, I'd definitely recommend this hotel as clean, modern, spacious, etc. The Eixample neighborhood was lovely and given more time I'd have liked to walk around it more. Hope this helps for anyone considering this hotel in the future.