You have to permit incomming traffic from the VPN pool network into the Local netwotk 10.x.x.x behind the PIX.
access-list acs-outside permit ip VPNPool-IPRange 255.255.255.0 PIX-Inside-IP-Range 255.255.255.0
access-group acl_outside in interface outside
route outside VPNPool-IPRange 255.255.255.0 VPN-Router
access-list NONAT permit ip PIX-Inside-IP-Range 255.255.255.0 VPNPool-IPRange 255.255.255.0
nat (inside) 0 access-list NONAT
should be something like this, but be aware that you opens a big security hole in your PIX as you permit all VPN Clients to connect behind the firewall.
Be sure that you have a tight access-list on your VPN Router.
sincerly
Patrick