Mac Mini with OS X Leopard Server

I have a few types of Home Servers, basically I have a HP ex475 MediaSmart Server ( Windows Home Server ) for Windows backup and Media Streaming etc , QNAP TS-109 Linux Server mainly for Torrent Downloads as it only uses 14w of power to run, and a Mac Mini OS X Leopard Server which I'd like to run some additional services that the other two can't do and relieve them from some tasks that they are better of not doing....

I'd like to run the following services...

1. DNS ( so that i can ping host names, and internet to be a slightly quicker )
2. Might consider DHCP to relieve it of my Draytek Router
3. Exchange Server like MobileMe Service for 2 x iPhones, 3 x Laptops mainly internally if via WAN as well will be cool
4. any other suggested service i should consider that leopard would give my network an good boost etc

Thanks

( how to setup DNS on a make with examples would be great )

Thanks again

A good boost to your network would probably to off load a lot of that stuff to somewhere else. For example, the DNS part - set your main router to OpenDNS. I don't think you want the traffic of DNS updates going back and forth through your network connection - you'll probably end up sucking more bandwidth than saving the time. As for DHCP, a good router at the front end of a home network should be able to do your DHCP services for you (more efficient and probably faster). For a good boost, trying getting a router that you can upgrade the firmware to DD-WRT or Tomato. I'm not sure what you mean on #3...do you mean you want to run your own email services?

I have a Draytek V2800VG Router + apple airPort Extreme Draft-N, & HP Procurve 1800-24G Gigabyte switch

Currently my Draytek is the DHCP , and DNS relay...
However i'm now thinking of removing leopard server off the Mac Mini and installing MS 2008 Server with MS exchange 2007