Where and how can I get the best international airfare deal ?

I want two tickets for a trip from Springfield MO (sgf) to Johannesburg, South Africa (jnb) travelling on or around June 25 and coming back on August 10.

So far the best deal is with Delta ($2750 all taxes incl.for us both) But I am sure we can get it for much better than that so now my question is where else can I look are there any really good travel agents or websites?Thanks for any advise.Where and how can I get the best international airfare deal ?
Someone else asked this question about SGF to JNB yesterday, I found them a cheaper flight on Delta. So if you want to look back you will see the answer.
Please check:

Tips:

a- use flexible dates

b- use alternative airports



http://www.hotwire.com/



http://www.cheapoair.com/



http://www.kayak.com/



http://www.orbitz.com/



http://www.priceline.com/



http://www.expedia.com/default.asp



http://www.farecompare.com/



http://www.farecast.com/



http://www.airfarewatchdog.com/



http://www.cheapair.com/Where and how can I get the best international airfare deal ?
I suggest trying this website to see if they have international flights that will fit your budget; www.everydaytravelconnections.com