FreeS/wan and Windows clients

I was planning on using Smoothwall to set up as a firewall router for a
clients' network - I had used it in the past with some success. I have
come to realize that their opensource release doesn't support multiple
external ip addresses and that is a requirement.

Part of the functionality I am looking for is to permit some users to
work from home and Windows clients can use L2TP/IPSec to VPN into the
lan and spent some time examining the documentation for this on
Microsoft's web site. I could always use 1 or more of the WinXP
Professional Workstations to handle the VPN connections but these
machines would have to be on 24/7, are limited to 3 concurrent
connections (I may never exceed this, but if it's as popular as I think
it will be, I might need to exceed this) and then there's the whole
issue of logging and security that is most difficult to monitor.

Thus, I am revisiting the entire option of firewall/router and FreeS/wan
and I am wondering:

1 - Is there an open source package that includes support for
kernel/freeS/wan updates that I could use and still be able to dmz
multiple external ip addresses?

2 - Is anyone currently doing this? Any recommendations? If I use say a
Red Hat distro, every time there is a kernel security errata (a little
too frequently these days), I would have to either rebuild the kernel or
rebuild the freeS/wan module - a PITA (makes a ClarkConnect system for
$125 look attractive).

3 - Is there any web pages / info that can tell me how to use openssl to
create certificates which are acceptable to Windows 2000/XP clients that
I can give to remote clients to use to authenticate themselves with
freeS/wan or should I stay with PSK?

Thanks,

Craig