Tube Integrated Pairing For Harbeth Monitor 30.1

Looking for advice to help a friend who is building a system around a pair of Harbeth Monitor 30.1's. His room is medium/small (14 X 16 X 8)and his listening habits mostly chamber music, jazz and acoustic singer-songwriter with some occasional rock and big band. He wants an integrated tube amp under $3-4K. It will need to have enough power to drive the M30.1's which are 86db sensitive but a fairly easy amplifier load. I'm thinking Cayin or Jolida and would be interested in hearing from those that have used these brands with the Harbeth line. I'd also like to know which models within these brands provide the best value for money and ease of use (i.e. he doesn't want to have to bias the tubes periodically, wants excellent build quality and reliability, etc.). I'm open to other brands but the Jolida and Cayin seem most appropriate from the little research I've done. Your input is appreciated.
A friend who owns the Harbeth M40.1 uses a Leben CS600 tube integrated with the speakers and often rotates it alongside some Naim solid-state amps. The Harbeth sounds lively with the Leben. Unfortunately, used prices of the Leben CS600 are above $4k. No experience with Cayin and Jolida but I guess they should do fine. Perhaps not as poised, delicate or refined as the Leben especially in the treble.

As a side-note, it may be useful to select a tube amp that has an upfront and lively sound as the Harbeth may sound a tad flat or dull(with warmer sounding amps) for rock and big band music due to their inherent character.
Audio Space make very good tube amps to relatively low cost. I would consider their models AS-8I or Reference 3.1 (KT88 a little cheaper than 300B version). It was Audio Space that made me a tube fan. Please let us know how it ends!

I am personally using Jadis with Harbeth and I can tell you it is absolutely glorious with the genres you are describing. Heavy rock, complex or compressed music is another deal though, solid state or very powerful tube amps are better for that. Good luck and have fun!
I wouldn't even think twice about the Rogue Cronus Magnum. Regardless what anything on the HUG tells you the Harbeths like more power than the 15 watts half those people are throwing at them. The Cronus Magnum will run him around $2100 and then the extra cash should be spent on a good power cord. Later on your friend can get some NOS tubes to play around with but I'd wait awhile. He'll be so floored with the sound he won't be thinking of tubes for awhile. A bonus to this amp is that it's made in Pennsylvania and they answer the phone when you call them and they care. I run the Magnum with C7es3's and I've heard the 30.1's. Perfect match for your friend.
Perhaps consider the little ARC VSi-60. I've heard good things about the synergy with this amp and Harbeth speakers.

I've been using the closely related Audio Research VS-55 to drive Harbeth C7es3's and now M30.1's - I think its a great combination. Tube sound, but with a nod to neutrality. Harbeth's are smooth and natural by nature and don't require any additional euphony to sound right. This amp sounds 'right' on every type of music.

New, the VSi-60 is just above your friends price range, but ARC stuff has stellar build quality and they're one of the few that will likely still be around to back up their product 20+ yrs down the track if required.

The only other sticking point is the manual biasing. This is ridiculously easy on the VSi-60 - external jacks, the same as my VS-55. My VS-55's bias is very stable, but tubes age so this still needs occasional (slight) adjustment to maintain optimum sound quality. It's so quick and easy with this amp it shouldn't be an issue. Typically, self bias amps are wasteful of output power compared to fixed bias (though some amps use the latter with with additional circuitry to auto adjust).
Interesting to see Audio Space was mentioned. I use Audio Space Nova 34 with Harbeth HL5S. Miles better than Audio Research VT100iii. I think they ae the same as AS8i.
The best sounding tube gear I used with both the SHL5 and 40.1 when I had them were from BAT and Manley. I preferred the BAT and would look for a used integrated from either company. The BAT will be tube pre/SS amp hybred.