DSL modem to use with LINKSYS WRT54GS?

Can anyone recommend an ethernet(not PCI or USB) modem that doesn't
NAT, and which will work reliably with the Linksys router that I've
been given? I already have a combined modem/router but the Linksys,
with it's open sourced firmware, looks interesting. Incredibly, the
linksys modem, the ADSL2MUE, does not work reliably with 54GS and is
really a simple NAT router.

Thanks

I've been told that the D-Link DSL-300T is the best solution - I'll
find out as I have just bought one too for the same application. Seems
to have the right specs & there is a gudei on adslguide.org.uk on using
it with the WRT54G