Best SUT For Van Den Hul Crimson Stradivarius cartridge

@lewm thanks for all the explanation.

I have read about 10-20 articles detailing all about impedance (47K)/square of turns ratio and how to modify the load using parallel resistors at the out put and in put.

If I use 1:10 turns ratio, the cart sees 470 ohms. I also know that, I can calculate the parallel resistors I need to use to decrease the loading.

What I am struggling to understand is the following, what is the best loading for a given cartridge. 

For example: the VDH Crimson Stradivarius says optimal load impedance of 20 - 600 ohms, which is such a large range.

I contacted VDH to tell me the exact internal impedance of the cartridge.

If they say the internal impedance of the VDH is 20 ohms. Then how do I use that number to come up with the best loading. 

There is no one single best load R.  The only rule of thumb is you'd like the load to be about 10X the value of the internal resistance of the cartridge, or greater.  When you go below the 10X ratio, you begin to lose both gain and HF response.  The lower below 10X, the worse the phenomenon. And paralleling resistors on either side of the SUT is fraught with compromises and side issues; I wouldn't do it.  I hope you do also know that if you start at 470 ohms, using a 1:10 SUT, you cannot achieve any load R greater than 470 ohms.  Any resistor you  place in parallel at the input will lower the load R.  Some swear by silver transformers and others prefer copper windings.  There is no consensus on that except silver is apt to cost a lot more than copper. Ypsi make a 1:10 SUT that is likely to be well suited to your phono stage; that's what I would recommend if you are willing to spend the big bucks.  Personally, I think the SLP05 is the weakest link in your chain, and I would go for a slightly higher gain linestage, if it were me.  But maybe I am being unfair; I haven't heard a Cary preamp in years.

@lewm 
Yes, I realized that one cannot increase the impedance by connecting resistors in parallel.
I have a Ypsilon MC26L SUT for Ikeda Kai cartridge which has 1:26 turns ratio. 57K||26x26= 84ohms. 
I belive the internal impedance of VDH could be 20-40 ohms and 10 times would be 200-400 ohms.
In my case, the ratio is much less and what I am hearing is very high, high frequency response and decreased bass. 
I am not considering changing the line stage because I read good things about the SLP05 and does a good job with other cartridges.

@bukanona I could not find any EMT STX 5/10 for sale. Is the EMT STX20 silver coil? It has 10db gain and will be enough gain for the VDH Crimson cartridge.

Kanchi647, when you connect resistors in parallel you drop the impedance, always. I agree entirely with lewm. You have an excellent phono stage. You do not need a SUT. You need a preamp with more gain or amps with higher sensitivity.
As for SUT's what you use for wire make very little if any difference except with price. You are way better off spending that money on a better cartridge or tonearm.