Hello, Since you can make and design power supplies , how about making a 350 Watts external power supply ? make it out put only 12V DC , and then make a small DC to DC board that converts to 5V and 3V needed to some parts in the pc. and make a box or frame that fits into the power supply cage of both ATX and SFX standards , and add as well a sticker if you want to stick this DC to DC board anywhere inside the case. you can design the case that fits in the power supply case with harddisks and SSD mounts . so we use that place for more storage ! the ATX Power supply is huge 150x150x95 you can imagine how many harddisks you can fit there ! or even maybe a FAN and Radiator ! beside the DC to DC board ! or even the choice to keep it empty for better and larger heatsink ! or more airflow ! This way will make SFF cases alot of empty space . and alot of external power even for a GTX 970 and i7 CPU system . The Geforce GTX 970 draws only 145 watts Max , the CPU and mobo around 150 Watts not overclocekd. so a 350 watts 12V is more than enough for this. and is possible . Thanks for your time !