Answer to "Trying to upgrade to Sierra, I need to upgrade WIFI card."I think the obvious point should be made that you can simply use a wired Ethernet connection and forego replacing the wIfI module. I live in Ontario and my ISP (Bell Canada) gives out WiFi Pods that have an Ethernet port on them, I’ve been using my WifI thru the wired Ethernet like this for months because of the higher 5G (AC) performance.
Answer to "G4 will not power up"The G4 Quicksilver came in 533MHz, 667MHz, 733MHz, 800MHz, 933MHz, And 1.0GHz speeds. ^^ this information is incorrect, the slowest Quicksilver was 733mhz.. the digital audio series: 466,533,667,733 and qs series: 733, 800 (single, dual), 867, 933, 1ghz (Dual) the DA + Quicksilver models share the most similarities + compatibilities of the powermac g4 series types, ie: bus speed, ram speed, hd speed, power supply, all compatible, motherboard is probably the same size + layout aswell