Windows and linux integration

Hi,

I have about 40 Windows hosts and 6 Linux servers. There is one 
Windows PDC to authenticate the users. The Linux server all run samba 
in Domain security mode. 

It's time to drop the NT box and move on but I am not sure what route 
to take. The client's need to have windows. I was wondering if it's 
possible to use LDAP/NIS or a pure Samba environment to authenticate 
the users. Currently I have to add each user to all the servers. It 
seems strange that I have to use an out-dated Windows box to 
authenticate user into a Linux environment which is what all the 
network is. I want to install Scalix as the SMTP server also.

Do I have to stick to a Windows authentication model? Is ADS and LDAP 
the best way forward?

Thanx,
Dp.