Which apps to mix on servers

Here are my apps in a W2K / NT4.0 mixed server environment:

Mail server
PDC
BDC
SQL server
NT4 TSE Metaframe 1.8 server
File and print server
Web server
WINS
DNS (w2k)

Is it advisable to mix mail+PDC or BDC?
Should WINS run on morethan one server?
How much processing and memory does a W2K AD Domain controller need in a mixed environment of 50 users? I’ve resigned to the fact that the web server and Terminal server must be dedicated servers but how much can you mix with the domain controllers?