SHL5+, Zu, Orangutan?

If you decide to try other speakers such as Zus or Orangutan, I would suggest retaining the Harbeth SHL5+. There isn’t any doubt that other speakers will give you more detail and are capable of sounding more spacious, open and dynamic at the frequency extremes but you may later miss the balance of the Harbeth. I find the tonal accuracy of the Harbeth to be superior to most speakers. Other than human voice where the Harbeth usually excel, I usually find the sound of percussion such as cymbals, striking of drums etc. to sound more realistic through the Harbeth. The sound of cymbals and hi-hat through other more revealing speakers usually sound a bit too tinny and metallic as if it’s boosted by EQ.

I have briefly tried the Macintosh MC275 with the older SHL5 model many years ago and didn’t quite like the sound. If I recall correctly, it’s a bit too heavy at the bottom and lacks the transparency, sparkle and dynamics. I’ve upgraded to the SHL5+ and am now using using something else to drive the speakers. I’ve tried not less than half a dozen of amps on the SHL5+ and there are few which made the speakers sound rather special. The SHL5+ can sound lacklustre with most mainstream amps out there. I would suggest exploring few suitable amps if you intend to retain the SHL5+. As everyone hears differently and has a specific preference on how they prefer their music to sound like, I think it’s best if the owner makes his own judgment on amp selection.

A mention on the importance of the source. I only have a single experience with Esoteric, an SA-10 player. I compared the SA-10 player to my Krell KPS-30i about 8 or 9 years ago and although there is a difference in sound quality, it’s quite marginal. I don’t listen to CDs too much these days as I am more into computer audio. A high quality DAC (apart from the amps) will also transform the level of performance of the system, particularly the SHL5+ speakers.

Good luck in whatever your decision. 

How about keeping the Harbeth speakers and changing tubes in the Macs?

I read that changing tubes in the MC275s was not beneficial.  Did you have a different experience?

YMMV but I have owned 275’s and SHL5’s but at different times. I presently own O96’s.

I was initially drawn to the 275’s because of the texture it imparted and over time that texture subjectively became mildly grainy to me. The SHL5’s are nice (Ive never experienced the plus version). I don’t know if the running out gas impression is the Mac or the Harbeth but I would consider a very nice a or a/b solid solid state amp if its the Harbeth’s you are trying to match to. The upper end on the SHL5 is not their best effort (when compared to, say their 30.2’s). What is it you are trying to build from? The amp or the speakers?

I was always building from the Harbeths, but I don’t know anymore. They really limit amp choices. After hearing the Zus and the Orangutans, I am intrigued. I only worry how it will sound once I get them home... 

@tswisla I haven't met an amp that didn't respond to tube rolling. Of course, there's always the possibility that you do not hear an improvement depending on tube choice.

Have you listened to Heck Direkt?

https://www.heco-audio.de/en/downloads/heco-direkt