Power amp for Reference 3A speakers?

That is a fine speaker. Personally, I liked tubes with mine. I used several different tube amps ranging in power between 1.5-5 watt/channel SET tube amps to 30 watt/channel P-P tube amps. All produced plenty of volume in my smallish room, but the 1.5 watt unit was near max volume.

What is your budget for amplification?

Enjoy,

TIC

These are indeed nice speakers .

I have auditioned them with tube and SS amps . Because they were designed for tube amps , tubes naturally sounded better , during my auditions .

I have heard these with a 5w SET amp , it was not really enough power .

The best is highly subjective .

I would suggest that you look for something that is quite resolving with good extension on both ends and decent detail . These speakers will show you what is delivered from your upstream components . They are capable of delivering crisp , clean and airy highs while putting out bass that you can feel .

You did not list your musical preferences or a budget . If you are not clear on these subjects , I would suggest a Primaluna Prologue 2 tubed integrated amp . The Prologue 2 is inexspensive , will sound good and allow you to experiment with a myriad of tube types . Coupled with the Di Capo's , you will be able to easily differentiate between upstream components and different tube types allowing you to seek the sound that pleases you . If you are new to tubes , the Primaluna's are self/auto biasing making tube rolling much easier and hassle free .

Then go looking for an amp that will give you more of an area that the Prologue is lacking with a minimal change upstream . The Primaluna's should be quite easy to sell .

This is the path that I am taking now .

Good luck .

There's a highly regarded Ars Sonum integrated amp for sale now.

I have no relationship with the seller.

Not knowing your budget, I agree with Saki70's recommendation. By all accounts it is a fine amp and they tend to be easy to re-sell if you don't love it.