Here is a list of commands that need to be performed. You man need additional configuration considering that most dsl providers require pppoe user and password setup. I will give you what i have on a pix with a pppoe provider. Its actually fairly simple
##first setup basic PAT access
login
enable
conf t
global (outside) 1 interface
!
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
!
##now setup pppoe
ip address outside pppoe setroute
!
#fill in your pppoe user and password below
vpdn group sbc request dialout pppoe
vpdn group sbc localname xxx@sbcglobal.net
vpdn group sbc ppp authentication pap
vpdn username xxx@sbcglobal.net password ****
!
dhcpd lease 3600
dhcpd ping_timeout 750
!
end
wr mem
!
You should also realize that your speedstream is natting you once and the pix will nat you again. Sometime you may have a weird issue surfing the net because of the double natting thats taking place. If it happens log into the pix and type clear xlate from priveleged mode. It will clear the existing nat translations .
Good Luck,