|Processor||i586-compatible x86 CPU or a supported ARM SBC with 500 MHz or better|
|Memory||512MB or greater|
|Storage||at least 4GB of harddisk storage|
|Network||at least two Ethernet network adapters|
Read more about System Requirements of IPFire.
Basically any x86 based system (with AMD or Intel processor) works very well with IPFire. The ARM architecture however is not that compatible. Please check out which single board computers are supported and which not in the ARM hardware section.
You cannot buy these systems any more.