Shocked. Need Opinions. How muck power do I need?

Is 40W enough? Yes, your 75W Cambridge EVO75 (89.5 db sensitive) is powerful enough to drive your Dali Mentor 6.

You need ~4w of power to drive the speakers at 10ft listening distance at 89.5db volume.

Unless your speaker are super hard to drive, don't get too caught up in the quantity wattage.

It's more important it's quality amplification that can actually reach up into its peak numbers with low distortion… because what's the point of the power if it's not really usable power. Pure wattage numbers is mostly useful for marketing and sales.

@swede58 well thats even better, meaning that 20W does the job 

@erik_squires, i will track down the pass article. i would add parasound as an amp which does well with challenging loads--during my brief forays with 83db planars my 125w hca1000 was surprisingly capable.

For every decibel volume increase above 86db requires double the power.

For every meter distance requires double the power.

Double the power will increase volume by 3dB (+23% perceived loudness)

Volume drops at double distance by 6dB. To keep volume the same requires 4x power.  To keep volume at 2m the same as 1m requires 4x power.

Not to sound repetitive but it is ALL about current, and damping factor! You only live once. Why go backwards? Is it just the form size? GanFeT solves that! Although that's NOT current as we all appreciate. Thats Pass Labs, Dan D, Mark Levinson, darTZeel... And many more... Hegel has unbelievable dampening factors of 2000!!!