Power conditioner

I love Nordost cables, but I would go with the Audioquest.  I use the PS Audio Power Plant for my main system, and I use a smaller Audioquest (I think it's the 1000) for my office system.  I'm pleased with both of the ones that I have.

I've seen reports of buzzing in some cases with the audioquest. Similar transformer tech can be found in a Bryston BIT20 or Torus RM20 with the added difference of isolation of the transformer to eliminate buzzing. Although the Bryston and Torus are industrial looking

No Shunyata or Synergistic Research?  I love my Shunyata Gemini 8 and MPC-12.  Have also heard Everest and Hydra Sigma.  If you can find a Hydra Sigma used, they are a steal.  Sorry no experience w these but figured I'd ask why you are only considering these brands?

They are very different products.  Keep in mind that the AQ 5000 is a 20amp unit and will need a 20amp power cord. 

I'm using the AQ 5000 on a 20amp circuit and I'm very pleased with the performance. 

The Audio Quest Niagra. It is a power condtioner. It is nearly universal that power conditioners have a very positive impact. There are very isolated instances where folks have really clean power and do not benefit from it.