Zu Soul Superfly

So, been a while and I’ve just done a fairly radical update to my system. Have binned my Naim CDX2 source after 18 years and the realisation that it’s now too harsh for my ageing tinnitus ridden ears allied to a plain simple lack of space for any more CDs. System is now Innuos Zenith 3 into Chord Hugo TT2 DAC going into a Naim 202/200 HCDR and NAPSC and all into the rather wonderful Zu Soul Superfly. 

Very long story cut short: The source is wonderful. The speakers are wonderful. The amplification is probably a level below what I need but holds its own reasonably well. However, at slightly higher volumes where the Superfly comes to life there is a lack of consistency and mid warmth. Rock in particular sounds under-powered. 
I am aware of an impedance mismatch between the speakers and the amp. It’s not the end of the world. I don’t tend to drive things loudly. Equally they have previously soared for years.  
Mrs. H. has ruled out valve amps for a variety of complex and not unreasonable reasons so I have several thoughts on which I’d like a view.

1 - loading resistors from Zu. I’ve yet to speak to Naim or Zu about this but people on other forums tend to the view that it’s a cheap thing to try but likely won’t make any difference. Your thoughts would be welcome. 
2 - if loading resistors then which ones? It’s been suggested 10ohm would be the contender but I’m unclear (and lack the technical knowledge) as to why. Again, thoughts?

3 - a replacement solid state amp which would work better with the Superfly. I’m well aware it was designed for valves but equally aware that several users found solid state amplification which sounded great. It’s been a few years since I’ve been on this thread but it seemed the obvious place to start. Who here continues to use their Superfly with solid state and what options are on the table. My funds will initially be limited to £2k but could stretch to £4k as the year progresses. 
If it helps then the Innuos source is pretty neutral and relaxed whilst the DAC is phenomenally detailed but also incredibly relaxed. I’d like to keep the detail but add some mid range. 
Thanks in advance. 

@mahughes have you ever tried running your speakers straight from the Hugo? I’ve heard of people doing that with efficient enough speakers. You need a special cable, but supposedly from the balanced out it can deliver 18W into 8 ohms. Might be an interesting experiment. 

Look for a Class A sweeter sounding SS amp if tubes are a no go - Pass/First Watt, Sugden. Maybe keep an eye out on the local used market.

@cat_doorman it’s an option mooted on a couple of other forums and indeed it’s suggested as one of the original design objectives by Rob Watts. However, I asked Chord directly and they’ve changed their minds as it’s not what the output stage was designed for. 
I sort of new Pass and First Watt were options. Must admit I’d not considered Sugden so that is something to look at.
I wonder what happened to the other posters who said they knew people had run SS with Superfly?

Interesting development (well, I’ve done further reading). 
Lavardin solid state integrated looks a feasible option. 
I’m getting the impression that 8ohm amps are fine with the Superfly and, whilst most prefer valves, there is a small subset of solid state that work really well. This looks like it could be a good match.