Power amp for Modwright LS100

I’ve been running a Pass x250.8 with great results. I’ve also tried the Black Treasure CV181’s ( 2 different pairs) in my LS-100 and have nothing but noise after a couple months use. Now have a set of Psvane CV181’s running which are almost as good as the Black Treasures, but are starting to get a little noisy after just a few months. I’ve gone through the old rectifier tube that was in when I got it in May of last year, plus a new one I replaced the old one with. This also blew the Synergistic Red fuse I was running in it. I’m done playing with tubes. Just the other day I bought an Ayre K-1xe to replace the Modwright. It arrives Thursday.
Good luck in your quest.

I have a Pass X250 with my ModWright LS36.5. My experience with a big SS amps with a tube preamp it's best to run balanced cables. My previous ModWright SWL 9.0SE was a little noisy too which is why I sold it and got the LS36.5. Your formerr LS100 has an XLR out, but it's just a cheater - not balanced.  Pass X250.8 with the Ayre K1XE should be very nice. Run balance cables if not.

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.