asterisk users - Jan 2006 - How to keep Asterisk (1.2) out of the media path

I have an Asterisk 1.2 install running on RedHat 9.  I have a bunch of
Polycom 501s co-locacted in the same building as *,  and some more
501s in satellite offices (also registered to my * server) .  Finally
I have some road warriors running XLites.

Ideally when a road warrior (XLite) calls a satellite office (Polycom
501), I'd like to avoid having Asterisk in the media path.

I understand that I'll have to avoid using the "t" &
"T" options in
the Dial command but I have some other questions as well:

1) Could someone confirm that I'll need to have canreinvite=yes in
sip.conf for both the Xlite and the Polycoms in order to bypass * from
the media path?

2) Does the Polycom & XLite support reinvite?

3) Does reinvite work if you're behind a nat?  i.e. if I have nat=yes,
does this mean I _have_ to have canreinvite=no?

Finally:

I have a suspicion that using a NAT router will prevent me from
eliminating Asterisk from the media path.  I am currently running a
Linksys WRT54G with Talisman to get QOS.  Any recommendations for an
alternate QOS router?  Ideally it will also support multiple
sub-domains...

I checked:

http://www.voip-info.org/wiki-VOIP+Routers

but couldn't see a _non_ NAT router with QOS (I don't need VoIP ports,
but maybe I'll have no choice)

Thanks,
Hugh