Hardware

I am currently running ClarkConnect for my home networking needs, but would like to migrate to mOnOwall for several reasons...

But I am unsure what hardware I should use for it... I have about 10 users (some of them are "power users"), and intend to use a 440BX motherboard with a P2 450Mhz, 256MB of SD-RAM. I have a dual PCI Intel NIC 10/100 (fxp).

Will this be sufficient for running without problems? The P2P traffic could be heavy from time to time. Though, it's only a 20mbps/1.2mbps ADSL connection - no need to have a higher throughput than 20mbps really then?

That should be plenty to run it.  Lots of room for the logs lol. And the ram is a good amount to handle the buffer of traffic.

should be more than adequate.

That's more than enough.  I have monowall running on a P2 350mhz with 128mb SD-RAM and it works great.

I am running  1.3b2 on a PIII 450 with 2x128 MB SD-RAM and a Kingston 1 GB CF-card on a ADSL2+ 25000/1500 connection. NIC's are two 3Com 3C905B. Performance and stability has been great. I did however experience quite high memory usage (90-95%) with only 1x64 MB RAM, and it's at 24% with 256 MB RAM. So it seems 64 MB is minimum, 128 MB is recommendable and anything above that is plenty.

This is a home network with 4-5 computers.

I am running  1.3b2 on a PIII 450 with 2x128 MB SD-RAM and a Kingston 1 GB CF-card on a ADSL2+ 25000/1500 connection. NIC's are two 3Com 3C905B. Performance and stability has been great. I did however experience quite high memory usage (90-95%) with only 1x64 MB RAM, and it's at 24% with 256 MB RAM. So it seems 64 MB is minimum, 128 MB is recommendable and anything above that is plenty.

This is a home network with 4-5 computers.

90% is high, did you tweak your m0n0wall installation to support more than 1000 concurrent connections? Cause that will definately increase memory usage from what I know. I'm currently at 40% memory usage as of now with my 64MB setup. Ram usage tends to increase all the way to 50%. I have not modified my m0n0wall install to use more ram. (enabling ram hogging features within the kernel or whatnot)