Which Upgrade First - Cartridge Or Phono Stage

Ok - I have about a $1500 budget to either upgrade my existing cartridge or upgrade my existing phono stage.

I'm currently running a Dynavector 10x5 on a VPI Classic 1 through a PS Audio GCPH.

I have read a lot of good things about the Soundsmith Zephyr and am seriously contemplating it but don't want to over-invest in the cartridge if I'm not going to hear the investment out of my PS Audio GCPH.

The same holds true in reverse.

If I go down the path of phono stage then one of my requirements is that it have XLR out since I just got done investing in new Nordost Heimdall cabling into and out of the phono stage.

So I'm really looking forward to the community's opinions.

Current system consists of the following:
Classe SSP-800
Classe CA-5100
Classe CDT-300
Thiel MCS1 (LCR)
REL Strata III (2)
My vote goes towards upgrading the cart first. I believe the PS Audio GCPH phonostage you have is resolving enough to showcase the difference in carts of varying quality. I think if you stick with your current cart and upgrade the phono, the difference in SQ is likely going to be nuanced/minimal and you will end up still having to upgrade the cart. If the GCPH were no tresolving enough then I would have said wait until you have saved to upgrade both.
The Dyna is a pretty good cartridge. I think you will see more bang for your buck with a better phono stage.

I think you will hear a greater upgrade in sound by changing the cartridge. You will hear the improvement with your ps phono stage
2 issues: 1. Its your money and you can spend it however you like but I think you are making a mistake with the Nordost. I'm not suggesting that it is not a good cable and/or you should not use it. That said, I think it is extremely foolish to buy active components based on what cables you have.If there was ever a wrong way to do something, this is it.
2. I had the 10x5 in my VPI and thought it was great for the money. I also had the low output 20 and it was a very big step up in sound quality. I know you have a $1500 budget but you might be happy with a 20 or something similar and may not need to spend that much. I would listen to a few things first before making a decision. If you call Ultra Systems/The Cable Company (fatwyre.com) you can arrange to try anything you like out of their lending library.
Thanks for the responses so far. I'm hearing what I thought might be the case with respect to the PS Audio GCPH and that I would likely get more bang for the buck migrating up the line with the cartridge.

xxqq250 - I appreciate your position regarding the cables. However, please recognize that I have to take into consideration the WAF associated with having just invested in brand new cables only to have to repurchase because I changed connectors. I'm pretty confident that there are quality phono stages that are balanced out that will not compromise my choice - although the options are certainly more limited. But, I will assure you that I'm more inclined to deal with the limited choices than to deal with an irate wife who really doesn't understand why I'm wanting to upgrade anything in the first place - it's a true balancing act.
I agree that given your situation, I would also go the cartridge route. I also have a Classic 1 and have tried the Dynavector 20X2L, Benz Glider SM and the Soundsmith Zephyr. All 3 are excellent cartridges, but I ended up settling on the Glider. I really liked the Dynavector, however in my system I have a little bit of a hum issue that comes more into play with the Dynavector's Low output (0.3 mV) vice my Glider's Medium output (0.8 mV). I liked the Soundsmith also, but sometimes found it a little more relaxed than what I was looking for.

I wasn't suggesting that you buy new cables, but that you don't build your system around them. What I mean by that is when you are selecting equipment, get what you think is the best sounding even if it is not the best match sound wise to the cables you have. You can always upgrade cables at a later date. Also, if you find a single ended phono preamp you like, you can just get an xlr to rca adaptors and use your nordost.
A good ( I mean, a real good one) Phonostage simply delivers you more information from any connected cartridge. But, getting a good Phonostage (one, which does not sound like a dead stone) is much more difficult than getting a good sounding cartridge. You would be amazed how many carts sound really good, even a Denon 103R can give very satisfying results (overall probably better ones than Koetsus for example).
But, there is not only one way to Paradise. It is far easier to design a good MM-level Phono Stage than a stellar MC-level Phono Stage, implementing the extra 30+dB gain required at a high level of quality does not come easily nor cheaply.
Based on this many Listeners may get better sonic results with a high output fixed coil cartridge (MM or MI) into a low-gain Phono Stage than a low-output, low-impedance cartridge (MC) into many MC high-gain Phono Stages. The lower the output voltage from the cartridge, the more capable the Phono Stage needs to be ( Price & Brain from the Designer ). To Design a world class Phono Stage (I write that, because every owner of anything thinks, his unit is worldclass) is not a trivial accomplishment. And Designers do something because they want to sell...not to make a religion out of it. Marketing will do that job much better...
So, back to beginning, better Phono Stages are able to extract more of the performance potential of the cartridge. Any cartridge. When you have ,bad luck‘, you can also hear what carts are good or not. Not everyone is mad to get that „kind of truth“..
I have a VPI Classic with a K&K phono stage and the Soundsmith Zephyr cart, along with a Synergistic Research Tricon Analog phono cable. This is an amazing combination! I don't have a pre-amp, but use a volume control on my phono stage direct to my amp. The K&K has XLR out, which is what I am using. The standard Maxxed-Out, which is what I have, should be a very substantial upgrade over your GCPH.

"The standard Maxxed-Out, which is what I have, should be a very substantial upgrade over your GCPH"

Amen to that!