Intergrated amp for Totem Sttaf

Have you considered a tube integrated? I've heard the Sttaf driven by solid state and thought they were very nice, but I bet tubes will really bring them to life. At 88 dB efficiency, the Sttaf should be fine with 50-60 watts. There's an upgraded Rogue Cronus (55wpc) in the classifieds right now that would be a nice match.

Are they easy to maintenance?

yes, but occasionally you need to replace tubes. This doesn't happen very often. Depending on use, it might be every few years.

What is the minimum watt can drive my speakers?

I found that 50 tube watts was enough to drive my 87dB speakers to a reasonable volume. Your Staff are 88dB. Doubling the power to 100 watts will only increase the SPL by 3 dB, but the difference in cost between 50 and 100 tube watts is huge.

A watt is a watt, but tube watts go further than SS. When a tube amp is pushed beyond its limit, there isn't a harsh break up like you hear with SS. SS clipping can damage your speakers which is why it's a good idea to have more than enough power when using them. Musical peaks can push a SS amp to clip. A tube amp breaks up much more gently and forgiving.