Why? What seems to be needed is a large current reserve to maintain the correct voltage across that low impedance.
I used to have the InnerSound Eros Mk-II. The best amps I found to drive them were the Monarchy Audio SE-160 tube/MOSFET monoblocks. They had a warm, musical character, with very lovely treble performance. They blended more seamlessly with the Eros than any other amps I tried.
The InnerSound ESL amp had plenty of power and pop, and the clarity was outstanding, yet it made for a thin and bright sound with the Eros. I would avoid it unless you'll have a lush-sounding tube preamp preceeding it. If you're not using a preamp and are using the InnerSound crossover/amp, then a tube/solid-state hybrid amp makes the most sense in my view (having tried a lot of different combinations myself).
Electrostatic speakers are not driven well by an amplifier that makes constant voltage with respect to load (i.e. most transistor amplifiers). This is because the impedance variation in ESLs is not due to the resonance of the speaker (where the constant voltage concept works fairly well). ESLs tend to sound better with an amplifier that tends to make constant power with respect to load as they will then exhibt flat frequency response.
Amps with contant voltage outputs will tend to sound bright on most ESLs due to the nonlinear increases in power that the amplifier makes as the impedance of the speaker decreases with frequency. Conversly, the amplifier power drops at lower frequencies where the impedance of the speaker is higher, making for bass-shyness.
In general, your best bet is a large tube amp, which is more likely to exhibit constant power if it does not have excessive negative feedback. Innersound speakers are a bit of a special case, as they have very low impedances that make them a difficult load for a tube amplifier.
This is often solved, as long as the power requirements are not too high, by the use of the ZERO. see zeroimpedance.com
Thank you for your reply. I am currently using a Brue Moore 70 watt tube amp that sounds very good. However all the imformation that I can find on Innersound suggests a very difficult load to drive so I am wondering if the Eros 3 would sound better with higher power amp. If I change I will look for a more powerful tube amp.