The barrier to entry is especially low since the consumer only needs to plug in a graphics card rather than build the entire computer.
Are the PSUs robust enough and have the proper connections for a high power GPU?
One of the main problems with console loading times is the CPU, an SSD only adds to the advantage.
Yes the power supply in those usually include an 8 pin power connector and is adequate for a mid range GPU (500-525w is standard). Literally just throw in the GPU and you are good to go.