Hello,
If you are really interested in getting security and having some functionality hosted yourself (mail/web) then I would strongly recommend you consider a DMZ for your hosting.This can be done a number of ways. But if you can spare an extra machine, this would be pretty good and save you about $1,000. Install smoothwall or ip-cop on it and you will have a dedicated hardware firewall. This is a great place to start.Now you can leave all your windows boxes on a LAN and host a DMZ as well.
In fact, I'm using Smoothwall right now for the current network, but I couldn't find anything to do with DMZ on the router? Although the ADSL router I have (not used atm, will be using it for the new network though) does have DMZ, used that without success in the past, although I'm a bit worried about putting my main PC in the DMZ all the time - I might want to log in my PC from work. Or I could just forward one port that SSH uses?
Cheers for your help Piers