Lee, I have no insight on what AbanteCart is using, and keeping up with what Google does requires at leas a Ph.D.! LOL
I can get on page one of Bing and Yahoo with my eyes closed. Google is a whole different animal.
What works today, doesn't work next week. They are constantly tweaking their algorithm to deliver more relevant content to the searcher, to hell with the developers!
Here is a great keyword tool, easy to use and very relevant.
http://www.bing.com/toolbox/keywordsAlso a paid service that is EXCELLENT in keyword development is spyfu.com
Again, it's a paid service and unless you have a lot of websites your promoting, it's a bit costly for just one or two.