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. 
Curious to still see this question 40 years later.
1) the most critical quality to a turntable is its ability to turn a record without imparting or passing through vibration to the record and tonearm.A poorer turntable will collapse dynamics and raise the perceived noise level of a record surface because of vibration transmitted and superimposed on the record groove signal. Another name for this attribute is resolution
2)  a tonearm must track rigidly and accurately while encountering variations in the X and Y axis's due to record imperfections in hole centering and record height. Bearing friction should allow slow movement across the record but damp oscillation at higher speeds... if you see the head of your tonearm quivering  during routine record playback thats a problem
3) cartridges are analogous to speakers, the patent determines their "house" sound, the stylus quality determines the limit of  resolution in
that family

Its is far better to focus your investment on the turntable,get a reasonably competent tonearm and use something like aninexpensive Grado  cartridge. 
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%

The turntable can make a large difference. I just upgraded from my old Rega Planar 2 to a Technics SL1210GR. I've kept the same cartridge and everything else is the same also. So much less surface noise and overall cleaner sound. 
There really is no difference in terms of pure performance. For every $2500 or whatever on a cart you can find $2500 in a turntable that will be a virtual tie in delivering sound quality. Where the difference comes in is over the long term. Your $2500 (or whatever, numbers aren't the point) cartridge will in 5 years (or whatever, numbers aren't the point) be worth zero. Your $2500 turntable on the other hand will be worth, well who knows? But not zero! Could even be worth more. You never know. Point is, one is a consumable, and one is not.  

So in my book if you are gonna go big it pays to go big on the table. Because then in five or ten when you replace the starter cartridge the better one you buy will be going on a better table. Where if you spent the money on the cart the next cart will be going on the lesser table. 

So these questions are like games where only Kirk (as played by millercarbon) knows enough to reprogram the game to win the no-win scenario.
I run a 43 year old DD table. Paid $45 for it 10 years ago. Cleaned and completely restored it. It’s competent in every way for speed, rumble, arm, suspension, etc.

Ive used a Decca Gold, Dynavector, various Ortofons, ATs, Shure, ADCs, Empires, Excels, Stanton’s,  Pickerings, Koetsu, and others. All the carts have a unique sound, and performed flawlessly.  The table and arm are not the limiting factors to great sound, as long as the table/arm are competent.