I purchased the 'hybrid" X1 with the smaller ps box. I could hear no difference between the two designs when I auditioned. According to Pass the supply is the same internally and the difference is only cosmetic. I actually prefer the smaller box unit. It allows me greater flexibility in placement- well away from sensitive components. I may be wrong here but it seems that 15 years ago most separate power supplies were designed with long umbilicals to keep them ( and their magnetic field) away from the preamp circuits and other components. Now days itÂ’s in vogue is to show off the supply in it's expensive milled case. Perhaps power supplies and internal shielding have developed so this is not as important?