Thanks everyone for the informative feedback!
Decided to go with power option E and 8580s only. Really cool solution with the PCB-panels! When I saw it I had already ordered case and panels from http://thebeast.co.uk/ though.
I have (finally) gone through the BOM and created my Mouser shopping list (can be copy/pasted here https://no.mouser.com/tools/part-list-import.aspx):
512-1N4148T50A|100
688-SKHHDT|50
604-WP424HDT|115
652-PEC16-4220FN0024|15
313-1250F-100K|4
161-MJ355W-EX|1
575-11044640|5
575-1104762841001000|10
502-PC722A|1
502-57PC5F|2
550-20301|4
710-860040478015|1
710-860241375002|10
647-ULD1E101MED1TD|1
647-ULD1H010MDD1TD|10
75-2C20X7R334K050B|1
581-SR215C104K|38
75-1C20C0G330J050B|8
505-FKP2.022/63/2.5T|16
581-SR211A102JAATR1|16
594-K471J15C0GF5UH5|8
858-36FR10KLF|5
264-10K-RC|10
610-BC337|1
512-BC547BTA|16
859-6N138|1
579-24LC512-E/P|8
595-SN74HC165N|5
595-SN74HC595N|11
579-PIC18F4685-I/P|4
774-ATS10A-E|4
511-L7809CV|1
532-577202B00|1
532-574502B03700G|1
919-R-78B5.0-1.5|1
660-MF1/4DCT52R5601F|100
660-MF1/4DCT52R1201F|100
660-MF1/4DCT52R1001F|100
660-MF1/4DCT52R1002F|100
660-MF1/4D52R1000F|100
660-MF1/4DCT52R2200F|100
Doest this look OK? Any suggested changes? Correct ICs, transistors? I went for longer lifespan electrolytic caps. Any opinions on those? Better options for the SID filter caps ( 505-FKP2.022/63/2.5T )?
I'm leaving the fan out. Got these heat sinks for SIDs and PICs. Might be too tall... How much space is there between the PCBs?:
https://www.ebay.com/itm/8pcs-14x30x8-mm-DIY-fans-cooling-Heatsink-Aluminum-Profile-Cooler-With-Tape/123021408514?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
https://www.ebay.com/itm/12pcs-10x35x10mm-Extruded-Heatsink-With-Thermal-Tape-Aluminium-Profile-For-DIP/112681555348?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
Also ordered this dirt cheap display. Measurements look good. Any opinions as to whether it will work with the PIC? If not; suggested display from Mouser/EU-supplier?:
https://www.aliexpress.com/item/1pcs-LCD-2004-20x4-Character-LCD-Display-Module-HD44780-Controller-Green-screen-backlight-forarduino/32691168548.html?spm=a2g0s.9042311.0.0.400f4c4dSOqlAZ
Also ordered a PicKit3.5 as I should be able to use that to program the PICs, right?
https://www.aliexpress.com/item/new-1set-PICKIT3-5-PIC-KIT3-5-PICKIT-3-5-Programmer-Offline-Programming-Simulation-PIC-Microcontroller/32847321104.html?spm=a2g0s.9042311.0.0.400f4c4dSOqlAZ
https://www.aliexpress.com/item/PIC-ICD2-PICKit-2-PICKIT-3-Programming-Adapter-PICKIT2-PICKIT3-Universal-Programmer-Seat/32730403341.html?spm=a2g0s.9042311.0.0.400f4c4dSOqlAZ
Wasn't quite sure how much current the 7809 would have to handle if I got 8 8580s sometime. Thus I wasn't sure how big a heat sink is needed. So I got two options and plan to mount the biggest one I can fit into the space between the PCBs.