I am pretty strong, and I recently carried my CODA #16 up the stairs to the office. That thing weighs about 110 lbs and I was thinking this is way too dangerous. It is not just the weight but how you need to carry the gear.
BTW - if the CODA 5.5 (or is it 6.5) is similar to the #16 as described in the other CODA thread then it would be a good match for the Harbeth. However, for my ears that match may not be perfect. I like the brighter AHB2 more with warm speakers like Harbeths.
I paired my Yamaha NS5000 with CODA #16 and got amazing results, say 95/100. That 5% was a little bit too much warmth with the slightly warmish NS5000 and the same warmish #16.
I now have the #16 in the office with my $1000 Magnepan LRS+. The LRS+ is a tiny bit bright. The LRS+ and the #16 pairing is incredible, 100/100. A better match for my ears than the much better NS5000 speaker and the CODA #16.
Another amp that you may like (built by CODA) is the Sanders Magtech. I got mine from Sanders for $4k used with 1-year warranty. The Sanders weighs about 45 lls and is sonically in-between the AHB2 and the CODA #16. It is very powerful amp, and I would bet great with Harbeth.
Another amp I am considering for my NS5000 is the SimAudio North Collection 761 or 861. The older Sim 860A that I heard was closer to the AHB2 than the #16 so that maybe a good match for me. The 761 is not too heavy.