Where is the significant point of diminishing returns on hi-end turntable?

For those that don’t know me I am newish to this game. Yes, I believe this chase for perfection in sound reproduction is a game. There are endless variables affecting the sound of every system and 100x that in opinions on each of these variables. I love cool $hit as much as the next guy but I am looking for an analog rig and I keep getting drawn into the seemingly endless "what about this option that costs tons more?". I started with a $6 to $10K budget and now I am considering a $25K setup (Table, cart and phono stage) after talking to a local retailer. I will be blunt, I want to be that guy in the Memorex ad from the 80’s that is getting blown away by his system (my impression is he is overwhelmed by the amazing sound coming from that speaker not the volume). Now that I have acquired some pretty descent stuff I am spending 15 plus hours each week listening and really enjoying this hobby. I don’t want to have any regrets and just be marginally satisfied with my setup but where do I draw the line? Back to my initial question; what is a reasonable amount to spend on an analog setup to achieve the best bang for the buck? I may be somewhat unique in that I don’t want to constantly be upgrading my equipment, I just want to buy great products the first time that are very satisfying and spend hours listening to great music. I don’t want to be the guy always chasing the next great thing.
It was maxell tapes, not memorex...

I have a clearaudio innovation with an universal arm and an air tight cart.  Lovely sounding.  And above all, ultrasound cleaning is a must.   Needs to be included in any table thinking
@desktopguy My father owned and operated a small audio visual production company my entire life. I was fortunate in that I would receive his hand me downs from time to time including a reel to reel in my bedroom when I was around ten years old He also worked in the radio business and often brought home albums on a regular basis. I still remember him giving me this album by this band named Foreigner. I think it was 3 or 4 months before it started becoming popular, very fun. Anyway, music has and always will be a constant in my life whether I am working, driving, cooking, reading, etc. I have an in-ceiling Sonance system installed in our home for background music along with a Sonos tied to Tidal. For serious listening I listen to my new gear I acquired at RMAF last month. I have averaged 2 hours a night since I installed the new Voxativ equipment. Tonight was closer to 4 hours.

I enjoy all genres of music as long as it is quality music and most importantly was recorded well. I have a keen ear for quality growing up in the studio. Tonight I listened to the Cowboy Junkies, Bill Callahan, Peter Gabriel, Pink Floyd, Chopin project, Yo Yo Ma (Goat Rodeo Sessions) and Anne Bisson. I also generally enjoy good female and male singers as well as classic jazz, blues, country to name some more. I have access to more than 5000 albums from my father’s radio days in his collection (mostly 50’s through the 70’s). Although many are not in great shape due to their frequent plays.

Lastly, I find it comical that many people on A-gon are questioning my reasoning or qualifications to own and operate a hi-end system. My father taught me how to use his very expensive professional equipment from a young age, showing me how to splice and edit 1/4 inch tape for example. How to use the mixing board and what all the sliders and pots controlled. So I am sorry I didn’t formally post my audio CV before eliciting advice from A-gon and have subsequently been called "rich", "stupid" and a "child". Think what you want, I have nothing to prove here. I am simply seeking advice and getting a lot of attitude - not from all but from many. I sincerely appreciate the actual well-intended advice.
I owned the innovation wood and had my benz LP-S on it (graham phantom II tonearm). It is a really well built, isolated table with a great heavy platter on a great bearing. Speed stability is best in class. Not a fussy turntable. The Benz LP-S is one one of the best cartridges out there - and I have a $15k goldfinger and MC Anna so it is in good company. The innovation is a wee bit Teutonic in character so the benz is the perfect cartridge. And if the dealer is willing to set it up and optimize everything that is worth a fee grand in "upgraded sound". 
If your also looking at phono preamps, you should consider the Perreaux Audiant VP3, it's even better than the Parasound JC3+.  I'm just saying in my opinion.
Hi mmporsche,

As several have noted above, auditioning and selecting an analog front end is probably the most difficult purchase in audio given the number of interdependent variables, and thus I wish you good luck in your search.  I think Inna puts forth some pretty good recommendations in his earlier post on price ranges, although I might allocate more budget to the cartridge on a percentage basis.  With that in mind, I offer some recommendations below at the price points that I find to represent the law of "significant diminishing returns," as referenced in your post, to provide some context on those proffered price ranges.  (Please note that if you consider used turntables / tonearms / phono stages, this would have a significant impact on the prices at which diminishing returns kick in). 

Starting with the turntable, the SME 20/3 is a good option - I have auditioned a few tables (and currently own one) costing 2-4x as much, but none of those tables were what I would call "significantly" better - the only tables I have heard that were that were so retail for $50k plus.  I definitely had my share of Memorex, "blown away" moments with the SME 20/2 (Solti Ring on Decca vinyl), and still remember it fondly.  And, it matches your requirement of a "set and forget" kind of table - the SMEs are no fuss and built to a high standard - I have referred to them in the past as the CD players of vinyl.  Finally, given the comparatively low value of the British pound, it presents a pretty good value right now.

Re: tonearms, the $4-5 range, where a number of long time stalwarts reside, seems to me to be the point of diminishing returns - e.g., the Graham Phantom, the Triplanar, and to a lesser extent, the SME V.   If you have a little more to spend on a tonearm, the Kuzma 4-point is a good option as well.

In my view, cartridges tend to be significantly dependent on one's personal preferences, and there are such a variety of options it is hard to propound recommendations without more of a sense of for what you are looking and what tonearm you would ultimately select.  For example, depending on what you value in an audio system and your tonearm, the diminutive Denon DL-103D may be all you need.   I note your dealer recommended a Benz Micro LPS, which is a pretty good cartridge, and I don't think you need to spend too much more to reach the point of diminishing returns.  Other options in that price range with which I have had good experiences include the Dynavector XV-1S and the Ortofon A95; the Clearaudio da Vinci v2 may also be a good option, but I have less experience with it.  If you are looking for a more budget-friendly option, the Shelter 90X is the best comparative value in cartridges I have found.

For phono stages, it is a bit more challenging to make a recommendation in terms of "significant diminishing returns," as I have not found one clear price point where the level of improvement drops off as price increases.  Taking for example some of the phono stages referenced above, the Herron is a very good candidate at around $3600, but I found the Lamm and ASR Basis Exclusive to be notably better (at 2-2.5x the price).  However, I would note I don't have as much experience in that $5-8k "sweet spot," so there may be some lesser priced options that would work for you.  Ultimately, given the comparative ease of demoing phono stages as opposed to the rest of the analog front end, I would tend to agree with folks above that you stick with the Parasound for the moment, and once you have settled on the rest of the front end, explore your phono stage options. 

Overall, I think at the price point you referenced above ($25k), you can get a phono system that you gets you within shouting distance of the best that is out there, which you can enjoy for a lifetime without any thoughts of upgrading.  If you go used (for everything other than the cartridge, which I recommend you buy new from a dealer), you can get there for $15k or less.  Again, best of luck.