[BUGA] networking advice needed

[David Bullock]

Hi folks, I'm hoping for a bit of networking wisdom, to solve some 
problems I have for my LAN's link to the wider world.

Here's the scenario:

   1. In building A, I have 3 hosts I use on a LAN (FreeBSD, Solaris,
      and Windows).

   2. In building B (100m away with a clear line-of-sight from A), I
      have a Telstra Home ISDN connection and an 'NT II Plus' NT1
      terminal-adaptor with both Serial (USB) and S/BUS connectors.  I
      want to run both BRI channels together, yielding 128kbps.

   3. It's likely that I'll install 'down only' (or possibly 2-way)
      satellite in building B to supplement ISDN in the future.  My
      likely satellite provider offers an Ethernet interface.

   4. It's also likely that I'll attempt to do VoIP from Building A to
      the switched telephone network using a service like Engin, or
      Internode's forthcoming NodePhone.

So in building B, there is some kind of router or system of routers 
which coordinates traffic between the gateway to my LAN (probably a 
wireless A/P, yet to be bought), and the ISDN/satellite co-gateway to 
the world, and which is sensitive to QoS classes for VoIP purposes (for 
example, not routing VoIP traffic via the satellite).

My research so far is leading me towards a (secondhand) modular Cisco 
1720 (or rack-mountable 1721), with ISDN, Wireless A/P, and Ethernet 
modules.   I am prepared to spend the money on a Cisco if it will do 
what I want it to, as it will be the most compact solution (physical 
size is an important consideration).

An alternative seems to be getting an external wireless A/P, and a 
dedicated *BSD box with 2 ethernet (satellite/wireless-AP) and 1 PPP 
(ISDN) interface.

Do these seem like reasonable approaches?  Any problems you can spot?  
Things I've forgotten?  Any comments about preferring one over the other 
(eg. is can *BSD handle QoS issues for VoIP)?  Any comments about buying 
secondhand Cisco gear, especially as it relates to software?  Any 
comments about VoIP traffic over wireless?

thanks,
David.