General Knoppix support for those who've read the FAQ at the Wiki
Dell PowerEdge R720 Server - 2x8c CPU,256Gb RAM, 128Gb SSD/3x900Gb SAS, Proxmox
$340.00
Supermicro 4U 36 Bay Storage Server 2.4Ghz 8-C 128GB 1x1280W Rails TrueNAS ZFS
$712.98
DELL PowerEdge R730XD 24x 2.5" Server Dual 750W Dual Heatsink - BareBones TESTED
$269.99
Supermicro 4U 4x Nvidia GPU AI Server 2.1Ghz 16-Core 192GB 2x10G SFP+ 2x2200W
$1250.00
Dell PowerEdge R620 Server 2x E5-2660 v1 2.2GHz 16 Cores 256GB RAM 2x 300GB HDD
$89.99
Dell PowerEdge R730XD 28 Core Server 2X Xeon E5-2680 V4 H730 128GB RAM No HDD
$389.99
HP Proliant DL360 Gen9 28 Core SFF Server 2X E5-2680 V4 16GB RAM P440ar No HDD
$196.95
HP ProLiant DL360 G9 2x Xeon E5-2690 V3 24 Cores 2.6GHz P440ar 32GB DDR4
$119.99
DELL PowerEdge R730 Server 2x E5-2680v4 2.4GHz =28 Cores 32GB H730 4xRJ45
$284.00
Dell Poweredge R640 8 SFF Server No HDDs/ CPUs/ RAMs/ Cards/Fan/PSU
$419.99