Traditional IRA vs SEP IRA

[jamazon]

Since I am self-employed, wouldn't it make more sense for me to open a SEP IRA instead of the traditional IRA where my yearly contribution is limited at 4k?

Another question I have is the need for a traditional IRA if I want to open a SEP IRA. I keep reading at the SEP IRA website but do not understand if I need to create a traditional IRA or not.

Thanks.