Yes its possible...
On your ADSL router you need set up port forwarding (from ADSL router to PIX)
You need forward following:
protocol ESP (protocol number 50)
UDP port 500
UDP port 4500
Let say that y.y.y.y is inside IP of you pix , outside interface of your router is f0/0 (with public IP) and inside interface is f0/1
ip nat inside source static esp y.y.y.y interface f 0/0
ip nat inside source static udp y.y.y.y 500 interface f 0/0
ip nat inside source static udp y.y.y.y 4500 interface f 0/0
interface f 0/0
ip nat outside
interface f 0/1
ip nat inside
Now all IPSEC VPN traffic for outside interface of router is forwaded to PIX and you can terminate there your VPNs
M.
Hope that helps rate if it does
