Both of the places you mention in the original post are the companies I use for tickets.
They produce a weekly e-newsletter so you always know in advance before tickets are going on sale.
If it is a big name concert then you'll probably be a big enough fan to know when tickets are going on sale and where from.
Also these are usually mentioned in the press as well.
When it comes to the big name concerts I'm yet to take part in an online "rush for tickets" that hasn't resulted in the websites going down so do NOT rely on them as the only way of getting tickets, have your phone ready.
We were after Kylie tickets for the Showgirl concert and it took nearly two hours to get our tickets.
This included numeros web site failures, getting through to the final stage and it throwing you back to the beginning etc.
We failed to secure Robbie Williams tickets twice - including Nebsworth, again due to the complete failure of the websites.
For some reason companies just don't seem to be able to build websites that can cope with rushes.
Personally if I were in charge I'd have a seperate server running for the big name ticket sales day, the website would have all fancy graphics turned off so you were more or less dealing with a text only site for the reservation before being moved over to yet another secure server for payment.
But alas they never ask me
![Smile :) :)](/styles/default/xenforo/vbSmilies/Normal/smile.gif)