Power amp for Modwright LS100

I've had my LS100 for about 2 years and haven't experienced any noise with the Black Treasure CV181s, nor any fuse blowing with NOS 5AR4 Phillips rectifier

I wouldn't think the LS100 would be noisy. Larger Pass amps can get a little noisy because of their high gain running single ended cables, so balanced is highly recommended on them. Both Pass and ModWright make great equipment and as always it's all about the synergy between any two components. I spoke to Dan before buying my LS36.5, and he stated on my Pass the LS100 would not be any quieter than my former SWL 9.0SE because the XLR Jack on the back of the LS100 is only a jack on a single ended output. Abucktwoeighty mentioned his LS100 was noisy on his Pass X250.8 which doesn't surprise me. As far as his misfortune of tubes goes, that probably comes down to not buying from a reliable source maybe?

Back to Bluejeans on the amp search. What is your budget? I don't believe your Harbeths are a difficult load, so I would recommend quality of power over buying a bigger cheaper amp.

A decent amp is just as important as rest of the components in the system.  I wouldn't skimp or settle on a cheap amp given what you're trying to put together.  

I highly recommend KWA150SE, you can buy one used at 50% or less off full retail. 

I own a pair of KWA150SE and it's a fabulous sounding amp especially when you pair it with a tube preamp. 

adg101, the tube sources I use are reputable. I'm listening right now to the Psvane's and they sound quiet today.  Some days the Black Treasures were just terrible, others not so bad.

I owned the LS 100/KWA 100se combo. Its was nice but might be a little warm for the Harbeths. I would go with something less warm than the KWA 100se or the Pass (but the .8's are not as warm as the .5's right?). If you can stretch to try the KWA 150se, it is not as warm as the 100 and might be better for the SHL 5+. Or try AR.