Virtual hosting behind a nat

Hi all,
maybe you can help me figure this out.
I am trying to host multiple webservers behind a nat.
I basically need two things:

1. showing the plain domain and not the ip

2. internal http servers must be able to see the users ip address

I've tried using mod_proxy but it shows the internal gateway address instead
of user addresses.
Should I use squid instead? Or am I just missing some mod_proxy config
option?

Thanks in advance,
Murdoch