Bill, the short answer is yes. Basically you will get more from whatever cartridge you use, when you have an improved tonearm. But that does not mean that the cartridge is unimportant. A better cartridge will still sound better on an improved tonearm.
About the mods, I think that the OL arm mods are the best ones, because of the better coupling of the end-stub, compared to Expressimo. So get the OL arm mods, and maybe an Incognito wiring loom for your arm. The best part from Expressimo, is their Heavyweight counterweight, and I would definitely get that, and put it on the OL modded RB600. You'll also need a VTA adjusting collar, and either the OL or Expressimo is fine for that.
Once you get all this stuff put together, then set the VTF dial to 3 grams(which defeats the VTF spring-factory default), and use a stylus-force scale to set your VTF. This will improve the sound because the VTF spring adds a tonal coloration to the arm.
When you set the VTA, only tighten the big nut with your fingers to a "snug fit" and not real tight. You will find that fiddling around with the tightness level of this big nut, that you can get a better sound, when you find the "right" tightness level. Never use a wrench on this nut. That would make it way too tight, and will "deaden" the sound quality. Just "snug" by fingers is just about right.
Of course, then you will have to play around with VTA to get it just right after your cartridge breaks-in.
These things should really get you somewhere. They are good mods, but will add up to some money.
If you could get a phono section that would handle a low output MC cartridge, you could then get a Denon DL103R, which would really knock your socks off, for only $230. You'd need one with about 65db-70db of gain, as the Denon has only .27mv output. Quite low. It will sound significantly better than even the Dynavector 20X and will destroy the 10x4. It would be great on a modded RB600. This is the "cat's meow" of low priced MC cartridges. Of course, the 10x4 is no slouch, and would also be a nice sounding cartridge, but not in the league of the DL103R.
If you are really enjoying your analog, and it sounds like you are, then you are going to need to get into the low-output MC cartridges sooner or later. If you can get your phono stage where you can accept these cartridges, it will broaden your horizons for cartridge selection, and will allow you to use something like the DL103R, which will give absolutely terrific sound for very low money. I have used one for the last few months on my rig, and believe me, this is one helluva cartridge. At only $230, it really makes everything else look very overpriced. You would not be disappointed with this cartridge, I can guarantee that. I have now moved up to a Shelter 501 at $800, but that Denon is about the best thing I've heard under that price. The Shelter is better, but the character is very similar. For the money, I still think the Denon DL103R is the best value in all of cartridges today.
A cartridge like that in a modded RB600 would give stunning performance levels, and would actually exceed the capability of your TT. The P25 would be holding you back at that point. How does that grab you?
Now before you go out and spend your money on these mods, you need to consider that these mods will cost upwards of $600. You could sell your tonearm, and buy an Origin Live Silver Tonearm for only $790, and this tonearm will kill any modded RB600. If you could get $450 for your arm, and only then spend $340 cash, you could get world class tonearm performance for less cash outlay. Also, what is very cool for you is that the OL Silver will drop right into your Rega arm-hole, and plug-and-play, with no fiddling around. Then you don't have to send your arm out, or take it apart yourself, and risk screwing things up, and get better sound than it is possible to get from an RB600.
This is important to consider because the arm mods you may be considering will cost near what the OL Silver costs. There is no comparison in the performance between the two.
Think about this.
About the mods, I think that the OL arm mods are the best ones, because of the better coupling of the end-stub, compared to Expressimo. So get the OL arm mods, and maybe an Incognito wiring loom for your arm. The best part from Expressimo, is their Heavyweight counterweight, and I would definitely get that, and put it on the OL modded RB600. You'll also need a VTA adjusting collar, and either the OL or Expressimo is fine for that.
Once you get all this stuff put together, then set the VTF dial to 3 grams(which defeats the VTF spring-factory default), and use a stylus-force scale to set your VTF. This will improve the sound because the VTF spring adds a tonal coloration to the arm.
When you set the VTA, only tighten the big nut with your fingers to a "snug fit" and not real tight. You will find that fiddling around with the tightness level of this big nut, that you can get a better sound, when you find the "right" tightness level. Never use a wrench on this nut. That would make it way too tight, and will "deaden" the sound quality. Just "snug" by fingers is just about right.
Of course, then you will have to play around with VTA to get it just right after your cartridge breaks-in.
These things should really get you somewhere. They are good mods, but will add up to some money.
If you could get a phono section that would handle a low output MC cartridge, you could then get a Denon DL103R, which would really knock your socks off, for only $230. You'd need one with about 65db-70db of gain, as the Denon has only .27mv output. Quite low. It will sound significantly better than even the Dynavector 20X and will destroy the 10x4. It would be great on a modded RB600. This is the "cat's meow" of low priced MC cartridges. Of course, the 10x4 is no slouch, and would also be a nice sounding cartridge, but not in the league of the DL103R.
If you are really enjoying your analog, and it sounds like you are, then you are going to need to get into the low-output MC cartridges sooner or later. If you can get your phono stage where you can accept these cartridges, it will broaden your horizons for cartridge selection, and will allow you to use something like the DL103R, which will give absolutely terrific sound for very low money. I have used one for the last few months on my rig, and believe me, this is one helluva cartridge. At only $230, it really makes everything else look very overpriced. You would not be disappointed with this cartridge, I can guarantee that. I have now moved up to a Shelter 501 at $800, but that Denon is about the best thing I've heard under that price. The Shelter is better, but the character is very similar. For the money, I still think the Denon DL103R is the best value in all of cartridges today.
A cartridge like that in a modded RB600 would give stunning performance levels, and would actually exceed the capability of your TT. The P25 would be holding you back at that point. How does that grab you?
Now before you go out and spend your money on these mods, you need to consider that these mods will cost upwards of $600. You could sell your tonearm, and buy an Origin Live Silver Tonearm for only $790, and this tonearm will kill any modded RB600. If you could get $450 for your arm, and only then spend $340 cash, you could get world class tonearm performance for less cash outlay. Also, what is very cool for you is that the OL Silver will drop right into your Rega arm-hole, and plug-and-play, with no fiddling around. Then you don't have to send your arm out, or take it apart yourself, and risk screwing things up, and get better sound than it is possible to get from an RB600.
This is important to consider because the arm mods you may be considering will cost near what the OL Silver costs. There is no comparison in the performance between the two.
Think about this.