Honest question about cartridge vs. turntable performance.


I’ve been a vinyl lover for a few years now and I have an ortofon black cartridge setup with an mmf 5.1 turntable with acrylic platter and speed controller. My question to all the vinyl audiophiles out there is this. How much difference does a turntable really make compared to the cartridge? Will I hear a significant difference if I upgraded my turntable and kept the same cartridge? Isn’t the cartridge 90%+ of the sound from a vinyl setup? Thank you guys in advance for an honest discussion on this topic. 
tubelvr1
I have to totally agree with chakster on his last post. The "noise" from a good DD turntable is vanishing low. Speed accuracy is superb.
What belt drive TT manufactures actually design and build their own motors? They just use an off the shelf product and in many cases it's a cheap product. They rely on the belt to smooth things out. Some state that they "modify" the motors, what's that mean, maybe shorten the shaft? And don't get me started on power supply upgrades. Some of the highly touted belt drives won't hold proper speed with out one. Isn't that the most basic job of a TT, to hold the correct speed?
BillWojo
Linn, the turntable manufacture argued that in a record player's hierarchy the turntable was the most important component followed by the tone arm and lastly the cartridge.
I think if you talk with a Linn dealer today, that same philosophy still exists.
The idea really makes sense, because you can not add additional information to a source, you can only reduce the information your trying to retrieve.(Or you can add additional distortion)
My advise is to find a dealer that will let you listen to different tt using lp's that are yours.
I think the Mobile Fidelity UltraDeck tt, is a great all-in-one set up.
You have to visualize the turntable as a system in which all of its parts working together in unisone gives you musical satisfaction . In your question if getting a given cartridge onto a better turntable will make the cartridge sound better is yes . Yes because if the turntable is better it will be.more inmune to vibrations making the task of the cartridge easier to track low level information. Being a system it is more complex then what I have explained but being all parts equal a better turntable should make a given cartridge sound better. 
As long as your turntable has the following figures:

rumble < 75 - 78 db,
wow & flutter as low as possible,
speed stability better than about 1%

and as long as your tonearm effective mass is a good match for your cartridge,
here are the approximate importance of the components:

turntable: 10%
tonearm: 10%
cartridge: 40%
phono amp: 40%

This ∆∆∆

It is easier to choose and to know what you have if you have numbers on the performance.
Otherwise it is just bla bla bla Words that confuse..

One thing that you can look at is if all types of adjustments parameters are available on the tonearm incorporated on the TT.

When cartridge is ~40% and you can't adjust for example SRA then you leave some performance on the table.. .. especially when you have advanced stylus shapes. (even better is if the TT has SRA on the fly adjustment). Now you can easily argument that a TT should sound better than one that cannot adjust it all.