Bookshelf Speakers?

Coincident Triumph. Single driver are all quite efficient.

WLM Diva Monitor (97db) are great with small tube amps and room-wise extremely flexible paired with the Diva Control unit.
http://www.wlm-loudspeakers.com/indexengl.html
Provided they are in your budget?

Some of Alan Yun's designs at Silverline Audio should be a great match. Auditions will be difficult to arrange, however.

Love my Triangle Cometes with my Primaluna PL2. You can find them used under $400.

Devore Fidelity Gibbon 3XL (90db/8ohm nominal)

Second the Triangles. Hard to beat.

Second the Triangles. You could also explore some floor standers like Triangle Antal and Celius... 92 db sensitivity and easier to drive than the Cometes.

Reference 3a or Coincident Triumph.90db + and a nice high impedance will serve the PL2 best.When taxed hard the PL@ can start to sound flustered,untaxed it is a sheer delight.

I have not yet heard the De capo's (reference 3A) but they are on my list. I saw a nice pair of Zu Audio Tones on here and gave it a thought. What kind of sound do they have? I heard the Zu Essence in town and was impressed but $$$$.

I love triumphs but sorry Celtic66, they are 2 way speakers. I'm looking at mine right now. Originally, Coincident had played with a concentric/coax single driver way before the triumph. I also have Conquests and Mini Triumphs. If you don't need much bass, the mini's are amazing. (my theater is coincident).

My second choice would be PSB stratus mini's.

I too have about 25 watts to play with. I sure am thinking about the Green Mountain EOS but not as a down grade especially from a Yamaha ns10m (he he). Also the deCapo I are on my short list. I'm just not too intrested in an overnight success type company, but that's just me. You might just hit pay dirt.
Intresting hobby we have here. Spend lots, itt'l help the economy! Happy hunting!!!