How much should a person spend to get a decent power conditioner?

A good conditioner will make your system sound more open and effortless, it will add weight and improve dynamics. In general however I haven’t found them to materially change soundstage, which is more a matter of low level noise better addressed via grounding solutions and the like. Rather against expectations I’ve never found conditioners to remove noise or so called grunge,

Exactly right. I'll add that due to the lower noise floor, there will be better separation between instruments. Also related is increased inner detail, you may hear effects and background studio sounds never revealed before.
 I like the more open and detailed imaging.

@whart. Glad you appreciate the quotation 😉

I have actually always used two stage power conditioning, a system wide transformer and a dedicated pair of conditioners for sources and power amps.

In my old Santa Monica set up I had a Equitech balanced transformer then conditioners (used to be RSA for the sources and SA on the amps, then moved to SR on both). Frankly I found balanced power to be more trouble than it was worth however so in my current Portland system I have a wall mounted Torus (which is balanced input but normal 110v outputs) and then a pair of SR 12 UEFs, one for sources and one for power amps

I also find that the SR conditioners are very sensitive to footers and the platforms they are on, vibration profoundly and negatively impacts power conditioners. My current preferred arrangement is GPA monaco stands to Marigo platforms, to Marigo footers

I must say you folks are very well versed and articulate with what are the potential benefits of a good power condition, to use the vernacular.  I am going to look into several items brought out in these discussions.  I noticed a couple references to not having your amp plugged into a power conditioner.  That seems counter intuitive to me.  I would think that it's one of the two most important devices (the pre/pro being the other) to have plugged in to a conditioner.  Can someone please expound on this?

The reason not to plug a powe amp int a conditioner is if it is current limiting. Of course they all claim that there will be no ill effects but many people find their power amps sound best plugged straight into the wall. As I noted there are some brands that I’ve found this doesn’t apply to but based on my past experience of never use a Nordost conditioner with powe amps for example, even though I liked them with my sources 

For grins last eve I decided to test ( double blind of course - hard to see out of both eyes after a few Reds ) the theory and well accepted claim that the power amp should not be plugged into the conditioner...

yup

front end into an Isotek, amp into a Furman PF15i

not as good as amp MC240 ( heavily modified by Mike Samra ) direct to wall

test CD - David Gilmour Solo
test wine : DAVIS Family Vineyards, Healdsburg CA

your voltage may vary