500 series preamps are a pretty popular item for discussion around here. I thought I would start a thread on the racks that hold these units. I'm going to give it a go as a first shot and as new or better information comes in I will edit this first post to try and make a pretty comprehensive list of options. At this point the list will use prices from Vintage King. They have the biggest selection I've found, and it's not my point to find the best price on any particular unit. I've only included units with phantom power and I've only included units with four or more slots. If someone else want to do a comparison of two slot units, be my guest. I should give some sort of spec on power, but it's not clear to me what the relevant spec is. Any suggestions would be welcome. So here goes- API 500-6B Lunchbox, 6 slots, Price = $424.00, Price per slot $70.67, Internal power supply API 500VPR, 10 slots, Price - $808.00, Price per slot $80.80, External power supply. Purple Sweet Ten, 10 slots, Price = $800.00, Price per slot $80.00 Internal PSU BAE 11 Module w/ PSU 48V, 11 slots, Price - $950.00, Price per slot $86.36, External PSU BAE 6, 6 slots, Price = $550.00, Price per slot $91.67, External PSU Radial Workhorse, 8 slots, Price = $1,399.00, Price per slot $174.88, Internal? PSU SPL RackPack API/SPL, 8 slots (4 API/4SPL), Price = $1,145.00, Price per slot $143.13 Tonelux V4, 4 slots, Price = $499.00, Price per slot $124.75, Internal PSU Again, I'm not familiar with most of these units and I have not looked at manuals, etc. So please correct any errors and I will update this first post. A lot of the units (e.g. the Radial) have extra features so this is not an apples to apples comparison. Hopefully it will be helpful nevertheless.