Recommendation for amp

With those Harbeth's, a little power goes a long way to helping them open up and sound great.  If you don't need built in streaming, I would look at the Rogue Sphinx.  It is in the middle of your budget.  Just plan to roll in some NOS tubes as the stock tubes are mediocre.  Add $200 to $250 for those tubes.  This is a 100w amp.  

If you need streaming, the NAD C368 with BluOS module would be my choice.  It is $1449 and a tremendous amp for the money considering the features and delivers 80w.  

I have no relationship with Rogue, I am an NAD dealer.  

truth is, many decent amps can work well with the baby harbeths

like all good speakers, they are fairly revealing of the source, so choose wisely

harbeths have good transparency but a warm overall tone, so if you like even more of that character then pick a tube amp - conversely, if you like more a see through, hear through, extended sound, then pick a good solid state unit

as harbeths have relatively relaxed treble presentation, even the lesser sharper sounding solid state units can sound pretty good... not as good as an ultra pure, more nuanced amp like a pass or ayre or hegel that will allow the speaker to do its magic in imaging and midrange palpability, but still pretty good

Audition and pick what you like. 

Assuming you will be at your desk while listening to the Harbeths, you wouldn't need a ton of power.  For a small footprint integrated amp, I would highly recommend the Rega Brio - it's half-size, 50wpc (8ohms), non-fatiguing sound.  

If you intend to sometimes listen from a distance and want to fill a larger space, then more power would be required.  

@smrex13 makes a great point, desktop application and small footprint desired... rega unit or psa sprout or w4s mint would work nicely - all with half wide chassis, decent sound

we all tend to spew out our favorites (myself guilty of this too) but it is important to note specifically what the op is asking for