Lyra or ZYX ?

I agree with Dover. His advice is a good one and his comment about the 3012 is also spot on.

Pani,

That is indeed the purpose of the SB option. My suggestion as to tonearm weights assumed that your cartridge would have one. To my knowledge (and on my advice) the US distributor doesn't stock any ZYX cartridges without it (except perhaps the entry level Bloom). A ZYX without the SB would want an even heavier arm, like 22g+. Such arms are not common, and are almost unknown among today's designs.

***
In principle, I agree with Syntax agreeing with Dover. ;)

A tonearm faces a fearfully complex array of challenges and tasks.

The challenges include very precise motion management in an ever-changing and largely unpredictable, 3-D environment plus the management of randomly induced vibrations across the entire frequency spectrum.

Using only those highly chaotic inputs for guidance, the tonearm is tasked with holding the centerline of the cartridge precisely above the center of the groove (wherever it might be at any given moment) while maintaining a constant downward pressure. Good luck with that. It's like a 3-D tightrope walk on a constantly moving and jiggling rope. Oh, did I mention? The tightrope walker must keep his balance bar precisely perpendicular to the rope at every moment, even though the angle of the rope keeps changing... randomly!

Got all that? Now, whilst doing all the above the tonearm must also transmit the most delicate, low voltage signal your system ever sees, with no distortions, inaccuracies or induced changes of any kind. Good luck with that too.

A tonearm is the most difficult-to-engineer device in audio, which means it's the component best suited to screwing things up.

Put a great cartridge on a crap tonearm and you'll get crap, because most of the great things the cartridge drags out of the LP grooves will be damaged before they even reach your phono stage, if they reach it at all. Put an average cartridge on a great tonearm and you'll get fine music, because more of whatever the cartridge is capable of will reach the phono stage undamaged. This isn't empty theory. It's the explanation of what I've actually heard, many times. I've owned several crap tonearms, one decent tonearm and one really good tonearm and a bunch of cartridges. In every case, a good arm/cheap cartridge combo has stomped all over a cheap arm/good cartridge combo.

Among my analog toys I've got a $100 MM, a $100 vintage arm, a $4K LOMC and a $4K arm. Put the $100MM on the $4K arm and it sings and dances. It's a decent little cartridge and the arm lets it play its stuff. OTOH, put the $4K LOMC on the $100 arm and it shrieks and howls. The crappy arm just can't handle the tons of information from the highly revealing cartridge, so it produces disortions. Of course the best combo is the LOMC on the snazzy arm, obviously, but if I could only have one of those $4K components there's no question which I'd keep. The arm would stay.

Doug and Syntax, I like your suggestions and can see very reasonable logic behind. But, are we not taking extreme cases into this equation. $100 tonearm with $4k cartridge is good for illustration but am I in that situation ? My tonearm is an SME 3012 Series2 with ATA (analog tube audio) modification. It may not be a top notch tonearm but it is still well respected, isnt it ? I paid $1.5k for it, the latest variant of this is SME M2-12R costing $2k. However there are lot of articles on the vinyl forums where people feel the older model was better. I do not know which is better but I would like to safely believe that they must be close enough hence the comparison. Mine is further modified by ATA (please read about them).

So, are we saying that a decent $2k tonearm is not worthy of a $1.5k cartridge (Delos or Yatra) ?

Or, am I being suggested that I should sell this arm, use my cartridge budget to top up and buy a modern arm like SME 309 and continue using my Denon 103pro ? And that will give me a better sound ?

Very reasonable question, Pani. Having no familiarity with any SME arms except the VI and V, I defer to those who have.

Pani - the SME has double knife edge bearings, that is the arm just sits on a knife edge ( but with 2 lines of contact ). A low compliance cartridge or cartridge that puts a lot of energy into the arm can "rattle" the arm in the bearings which leads to a smearing of the sound. Furthermore the SME armtube is quite resonant and again resonant colourations mask detail. Finally the detachable headshell lacks rigidity, again smearing the sound.
Typically well designed gimbal bearings will have significantly less rattle if correctly designed, and are in general much more suitable for low compliance or cartridges that impart lots of energy into the arm.
The most rigid bearing, ironically, is in a fact a unipivot, the stylus drag pulling on the arm imparts a rigid coupling between the unipivot bearing point and cup. A correctly designed self centering unipivot bearing will maintain this rigidity even as the bearing wears whereas in a gimbal or captured bearing, wear will result in loose bearings and chatter.
I would expect the Graham unipivot for example to give a far more precise sound from the Denon than the SME. In general I have found unipivots to impart more fluidity to the sound compared to a gimbal bearing arms.
There are always exceptions but I would not run knife edge bearing type arms ever unless I was using a very compliant cartridge that does not put energy into the arm.