Is 50 wpc SS NAD enough to power Spendor SP1?

Good to go. No prob.

The Germans have a great word for that.......jain. Yes and no. Drive yes, will you fall in love with the sound, no. These speakers really like very heavy stable current. You throw something really solid behind them and they wake up and show you the micro dynamics and imaging. Otherwise, un-involving comparatively.

Find some really good power and be happier.

Celtic66 nailed it.

To do your Spendors justice, look to a better integrated amp.

For example the last two audio expos I attended had Spendor speakers driven by EXPOSURE electronics and VDH cables .

The EXPOSURE integrated amp will smoke the NAD. I've personally owned the C370 in a prior "B" sytem and know its signature sound, warts and all.

+ 1 to the Celtic66 prompt to look elsewhere.

I owned SP!'s for a long time. You really need a minimum of 100 watts/ch of high quality amp to do them justice.

Neal

SP1 will just work fine. NAD has soft clipping so it can potentially perform as more powerful amp.
None can assume weather you'll like the sound or not till you will try it and see for yourself. It's not hard to sell amp for upgrade when the mean time passes by.