How good does a TT have to be for a good cartridge

I suppose an explanation is warranted. The Scout has a JMW-9 tone arm with a 20XHO Dynevector cartridge. The Phono stage is a Grahm Slee Gram Amp 2 SE which has gain suitable for MM/HOMC carts. My Preamp is an AE-3 modded with top notch caps and hexfreds, I use Sylvania Metal Base 6SN7W s and a variety of other really good 6SN7s in it. The pre feeds Opera Consonance Cyber 800 tube Monobloc power amps which power Focal/JM lab Electra 936s. Cables are HomeGrown Silver Lace ICs, Audience ICs, Cardas Golden Ref Ics, and Jena Lab copper braid speaker cables. PCs are eccentric custom made ones with fancy RFI/RMI pixie dust and braided ground wire shielding for the amps. Audience and Cardas PCs again on the other stuff. The sound is really wonderful. I was only asking that question out of pure curiosity.
The MMF 5 system is a WAF centric one. The cart is a Goldring not sure which one.. (I think maybe the 1042 or the lesser 1012X, it came pre-mounted on the table??) the Phono is not so great it is an Australian SS mini box piece by Redgum. The amp is an integrated Jadis DA-60 (tubes are GL KT-88s Sylvania 5751s and Amperex 7316s) and the speakers are Von Schweickert VR2s. The cables are a mediocre mix. The sound is not nearly as detailed or transparent on this set up as I like. However, it is quite nice, very smooth and easy on the ears, but that amp deserves better in all honesty. The Phono stage would be an easy target here, perhaps I get a better one for the Scout system and use the Grahm Slee in this set up. I don't have the were with all to improve on this system right now but some day.

You can't go wrong upgrading the phono stage. The Gram isn't bad but can definately be improved upon. I suggest buying the best you can so you don't have to upgrade again later.

"My local dealer did a blind testing of carts on a very hi res system...the verdict/?...many couldn't distinguish between a 200 dollar cart vs 2k cart al things being equals...save your chips...other hi rollers will dispute this...but everybody wants to justify their purchases...even at the hands of clever marketing"

I've heard the same arguement for amps (so long as they're not clipping), cables, and DACs. To my ears, everything makes a difference. I may not agree with the hifi rags and some users as to the magnitude of the differences, but they definitely don't all sound the same IMO.

I've heard cartridges compared where all things were in fact equal, and heard a difference every time. This wasn't once or twice either.

Cartridges work by vibrations. Will every cartridge pick up every vibration exactly the same way? Different styli fit into grooves differently. Different cantilevers and their suspensions will allow those vibrations through differently.

This is the first time I've heard all cartridges sound the same though. I thought turntables and cartridges were immune to this nonsense, but I guess you learn something new everyday. Quite possibly the most absurd 'all x components sound the same' agruement I've ever heard.

How's this one - assuming correct placement and room acoustics, all speakers sound the same, except for low frequency extension.

I'm currently trying to answer this very question. Recently acquired a Dynavector XV-1s for my Scoutmaster Signature table (w/ JMW9 sig arm). I'm A/B this with the prior Sumiko Blackbird cart. One might think it should be a slam dunk with the XV-1s, but there's actually a number of traits about the Blackbird I favor over the XV-1s. This may be a result of better synergy with the table, the arm, the phono pre (EAR 834p deluxe) or all three. I actually have 2 JMW 9 sig armwands so that I can A/B easily. So, the jury's out, for my tastes. About to also mix it up even more with a Herron VTPH-2, just to see what a phono pre upgrade might offer....

Your vinyl set up is only as good as the weakest link. Instead of focusing on a $3k+ cartridge, work on isolation-cables and synergy between the cartridge and phono preamp.