Buy core 2 duo, intel motherbaord with intel nic, and fast hdd. 1 GB of ram is more than enough if you run dude on ROS. I have system with pentium D daul core procesor, and seagate 7200.11 hdd, and i think hdd is botlenecking everything. Now it makes 6000+ sector writes per second. So if i had enough money, i would store database on some new ssd, like Intel X25-M Or OCZ vertex (30 Gb). Or try setting up short stroking
I have about 300 devices on my dude su it uses weakly:
CPU: Max:34% Average:30% Current:27%
RAM: Max:174.02 MiB (9.1%) Average:161.78 MiB (8.5%) Current:174.02 MiB (9.1%)
HDD: Max:779.40 MiB (0.5%) Average:680.46 MiB (0.4%) Current:779.40 MiB (0.5%) (i put my backups in routeros file system.)
Max In: 338.40 Kb Average In: 316.83 Kb Current In: 312.90 Kb
Max Out: 765.09 Kb Average Out: 481.84 Kb Current Out: 517.77 Kb
Hope this data helps.