Power needed is primarily a function of how loud you want to be able to push them (within their mechanical limits, of course). Vandersteen recommended amps with an RMS rating of 100--200 watts. Side note - 200 watts provides only 3dB more output than 100 watts, and 3dB is the smallest increment of change in loudness that would be obvious to the average person.
So, you should be looking for an amp rated at 100 watts per channel RMS or more, measured from 20-20kHz. More power than specified is not a problem, since you have control of the volume knob! If the speakers sound like they are straining, turn it down.
As for current...the amount of current drawn is a function of voltage (controlled by the volume knob) and load (defined by the impedance of the speakers). The Vandersteens do not present a particularly difficult load...4 ohms at minimum. So, you need an amp rated for 4 ohm loads.
I'm never quite sure what is meant by recommendations for "high current" amps. The fundamental question is whether or not the amp can handle the load presented by the speakers. Yes, some amps can deliver the current demanded by, for example, a 2 ohm load. Does this make them "high current"? I guess so, assuming the speakers in use drop down to that impedance at some point on their curve. But if using that amp with an 8 ohm load, is it still a high-current amp?
I suspect that what is really meant by "high current amp" is "capable of supporting low impedance loads". And of course that's only useful if you know how low of a load can be handled. In your case, 4 ohms is perfectly adequate.
After meeting your power requirements, it comes down to sound quality. The Vandersteens deserve a clean signal, with minimal coloration. In my experience, the pre-1976 (or thereabouts) Sansui designs were more colored (warmer sounding).
Given that you are happy with the sound of your Vandersteens with the AU-9500, but wondering just how different they might sound with a different amp, I would recommend trying something significantly different...maybe something from the Crown XLS series. After hearing good things about them, I picked up a used XLS 1002. Pretty impressive performance, especially given the low price point. Lots of power, capable of handling low impredance loads, and very clean sounding (at least to my ears).
I have Vandersteen 2Ce Signature IIs in my main system, powered by a rebuilt Sansui AU-919. I think it does a fine job with them. I used the 919 as a preamp when experimenting with the Crown, which also sounded good, and perhaps provided a bit more detail at the lower frequencies (or maybe I was just over-analyzing!).
Note - I also run a pair of Vandersteen subs, which - with their crossover arrangement - reduces the demand on the main power amp (by reducing low frequency reproduction from the main speakers). My point is that in this scenario, the 919 has more available power than it would if pushing the speakers full-range.