Need Cartridge Suggestion for Michell Tecnodec

Hello, I have a J A Michell Tecnodec with the bundled Rega RB 250 arm. My phono pre is a PS Audio GCPH, with an ARC LS 25 preamp and a BAT VK55 amp.

At the moment, I am using a Dynavector 10x5, but I am feeling that it is too entry level to really make the vinyl sound amazing.

My dealer is recommending the Lyra Delos. I am intrigued by the Koetsu Urushi (and I have a friend in Japan who can help me get one for half the US price).

The truth is, I have no idea. My dealer is the one who will mount the cartridge, and I believe he does a very good job with it. But I do not have any experience mounting cartridges. I have no place to audition cartridges. So this is really sort of a blind purchase. Please Advise!
Your displeasure probably comes from the arm. Replace it with something more ambitious.

At the very least, get a rewire and new end stub and weight.

No point in putting great tires on a Yugo.
Download the Rega arc protractor from vinylengine and you'll have all you need to align a cartridge on that arm.

(You'll have to register at vinylengine before you can download.)

Did your dealer throw in the Michell VTA adjuster? You need some kind of VTA adjustment as the 10x5 is taller than Rega carts. The dealer may have already done this, but you may want to experiment with adjusting the level.

I had a 10x5 on an RB300 mounted on my Gyro and thought it was a very enjoyable combination (until I KO'd the cantilever.)
I would look at upgrading your arm before the cartridge. It is easier to get better performance from a great arm and cheaper cartridge combo than a cheap arm and expensive cartridge combo.