General Knoppix support for those who've read the FAQ at the Wiki
HP Workstation Z640 2x Xeon E5-2623V4 32GB Ram 2x 256GB SSD Quadro 2000 Linux GA
$212.49
Lenovo ThinkStation P520 Workstation Xeon W-2123 3.6GHz 16GB RAM 2TB WIN10
$209.99
HP Z420 Workstation Xeon E5-2690 v2 3ghz 10-Cores 64gb 512gb SSD 4TB Win10
$239.99
Intel Xeon E5-2699A v4 SR30Y 2.40GHz 55MB 22-Core LGA2011-3 CPU Processor
$269.99
Intel Xeon E5-2680 v4 SR2N7 2.40GHz 35MB 14-Core LGA2011-3 CPU Processor
$14.99
SR1XP Intel Xeon E5-2680 v3 12 Core 30MB 2.5GHz LGA 2011-3 Grade A Processor
$4.50
Intel Xeon Gold 5318N 24-core 2.1GHz SRKXG Processor
$300.00
Dell Precision T5810 Xeon E5-1620 v4 (3.50GHz) 32GB RAM, No OS, No Graphic Card
$100.00
Dell Poweredge R630 2x Xeon E5-2680 v4 2.4ghz 28-Cores / 128gb / H330 / 2x 1TB
$294.99
Lenovo Thinkstation P510 E5-1620 V4 16GB RAM 512GB SSD DVD Quadro M2000 W10 Pro
$164.95