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The Paul Buff Einstein's are smaller than your big White Lightnings, but not much lighter, and still have about the same power, so they are not of much help. But the fairly new Mini Vagabond power packs that Buff sells are much lighter than the old Vagabond power packs, and reasonable in price. You might want to consider the Mini Vagabond's with your current White Lightnings to see if it can work for you. It is not going to be as easy to handle as some of the intermediate portable pack units like Quantum, but it is a way to get going for a lot less money since you have your strobes and modifiers all ready. Worth considering in any case. A 5 pound strobe on a good stand with the Mini Vagabond attached to the stand as a counter weight is pretty portable to move around.
Eventually you could consider Einstein's as an upgrade if you want to be able to adjust power remotely, but that may not be something you ever need.
I happen to use the Profoto Acute B 600 pack system for my portable needs, but if the Einstein and the Mini Vagabond had been available when I geared up for portable use, I would have gone down the Buff road rather than Profoto. The current Profoto portable units would be way over your budget, plus you would need to adapt to a different modifier mounting.