Some reading here (have you found and read the review and the comments there?) suggests that you can use the R3 as a desktop speaker. You need to get them away from the back wall a little, I'd guess fully plug the port, and a desktop stand will be useful as sitting them on the desk directly will probably have a negative effect on the bass (llke sitting a bookshelf speaker on the floor).
This being ASR, I note that the speaker looks a really good pairing on specs with the well-reviewed Benchmark AHB2 - if you can afford it. That's a power amp of course, so you would need a source with volume control, or a preamp. Any of the decently reviewed integrateds here with Hypex or Purify class D modules will probably do the job as well, if you want an integrated amp.
Apollon mentioned above look like a good option for an EU purchaser. Power amps, again, and I'm sure they can advise on the best match and get you over the line.
If you add the KEF subwoofer and cross over close to 80Hz, you can avoid that 3 ohm dip and use a less powerful amp. I know someone who has done that and uses a mid range Denon amp, who claims good results. I'll get to listen one day, I'm sure, but not yet.
With speakers on a desktop, you might find a full sized integrated amp too big - bear that in mind.
Good luck!