I saw Foo Fighters at Wembley Stadium. The sound was terrible, for the support acts it was dreadful. That's probably the biggest rock band in the world and they didn't sound great.
Best venue I go to for sound quality is the Fleece in Bristol, capacity of about 300, brilliant sound, never more than 5 seconds from the bar and they get some awesome bands. Killing Joke at the Fleece was probably the best night of live music I've ever had and it cost me £22.
Dave Grohl should have stayed in Killing Joke.