Based on your info, the PIX506E is sitting between your internal network and internet.
On PIX, you need to do address mapping of your internal server on remote LAN. But before that, what's the connectivity looks like from your HQ to your remote servers? Any NAT/address translation in between? Or since you mentioned about VPN3K, and LAN-to-LAN/site-to-site VPN involved?
If no, then do:
1. Static mapping of your remote server private IP to Public IP. This is to enable internet users to access/reach the server through your PIX506E:
static (inside,outside) xx.xx.xx.10 192.168.100.10 netmask 255.255.255.255
*xx.xx.xx.10 is your Public IP
192.168.100.10 is your remote server IP
2. Open/add access-list to your PIX's Outside interface to enable traffic via whatever TCP/UDP port to reach the server:
access-list outside permit tcp any host xx.xx.xx.10 eq www
access-list outside permit tcp any host xx.xx.xx.10 eq https
access-list outside permit tcp any host xx.xx.xx.10 eq sql
access-group outside in interface outside --> bind ACL to outside interface
PIX 6.3 Guide:
http://www.cisco.com/en/US/products/sw/secursw/ps2120/products_configuration_guide_chapter09186a008017278e.html#wp1069973
HTH. Pls rate all post(s)
AK