I had all the Vader guitar cabinets and used them for about a year. Basically, they are one trick ponies and only work well with certain amplifiers, IMO. They were created with the buzzy nature of the Peavey XXX in mind, and when paired with similar amps like the 5150, they can sound incredible for heavy metal. They seem to tame the fizz that people often complain about from those amps.
But, outside of heavy metal and buzzy amps, they are far too sterile and bassy to really do much. If you're into heavy metal, low tunings, and have an amplifier along the lines of the 5150/XXX, then it's worth grabbing. I haven't had a lot of time with a 5153, so I'm not sure about that one in particular. They are fairly easy to resale too if you're not into it.
I loved Vaders with my 5150, but once I sold it, the cabinets had to go too. I never even considered changing the speakers, because I can't imagine the custom designed Eminence Legends having that much resale value.