Okay Bill, to answer your questions. The difference between a modded Rega RB600 and an OL Silver is quite large. Far, far more than the price difference. Whether you think it is worth the money is a personal decision, but to give you a guide, let's look at some things. First, an OL modded RB600 is not as good sounding as an OL modded RB250. Primarily because of the VTF spring on the 600. The modded 250 is the best sounding of all OL modded Rega arms. The OL Silver is about twice as good as the OL modded RB250.
Now this is all relative, because the Rega arms are already some of the better sounding arms available, and are good value before you even start modding. When you start with the mods, the 250 is the best one to mod, because it can come out at a higher performance level, than any of the other Rega arms, after modding. A modded 250, will sound better than a modded 900. The reasons for this are all explained on the OL website. A modded 250 is known as a "giant killer" arm, because it performs near the level of some of the best arms around, for alot less money. It is a great value for the dollar, and I by no means am knocking this modded arm. It is one of the better arms out there, and would be at home on a very high priced turntable, and sound great.
Now when we get to the OL Silver, we are in another category altogether. This arm was designed from the ground up to be better in all respects than a modded Rega arm. And it is. It gives performance at or above just about all of the top arms out there. It IS one of the top arms out there. So, you can choose, do you want "near" to the top arms, or do you want "one of the top arms".
Now getting to the Expressimo Audio mods, they are some good mods, and are very similar and close in performance to the OL mods. I would say that some people might not be able to tell the difference bewteen them. I think that the coupling of the OL end stub being minimal in contact with the arm tube, gives the OL stub an edge in performance over the Expressimo. Not alot. The Expressimo Heavyweight is definitely the counterweight to get, whether you get an OL end-stub or not. The Expressimo or OL VTA adjusters are about the same. The Cardas wiring in the Expressimo is probably a little better than the OL wiring. All-in-all, there is not alot of difference there. Both are good.
If your budget allows only $300 incremental spending, then maybe that points towards modding a little at a time. I'd do the VTA adjuster first, then the end-stub, then the wiring, then the Heavyweight.
About the cartridge and phono stage, if you have a high gain line stage that can add about 25db to the 53db of your phono stage, then you could use the Denon DL103R, without a transformer. Viridian pointed this out to me on another thread yesterday, that I was not considering the gain of the linestage, when I was calculating total phono gain. He was, of course, correct, and I am now mentioning it to you. If you can get a total of about 75db-80db out of your phono stage and preamp combined, you could get into the ballpark. You may have to turn up the volume a little higher to get normal SPL.
Now, getting back to your turntable, while Inna was less than diplomatic, he was actually correct in that you could get more performance increase by improving the table, than you can by improving the arm or cartridge. This is the case with ANY table, not just yours. It is an analog maxim. However, there is no rule that states that you cannot improve your arm, with the idea that eventually you will transfer it onto your next table upgrade. I think that this is what you are doing, and you will upgrade tables in the future, I'm sure. Because I can see you have the "fever" and you will want to improve in that area as well. In the meantime the P25 will serve as well as it can. Very few ever reach the level where no upgrading is possible.
Now to make a summation here, if I were in your position, with the money budgeted in $300 increments, I would first put my RB600 on the Audiogon, with a price tag of $495. If I could get it, or near it, I could then take my $300 cash and add it to what I got from the sale of the RB600, and order an OL Silver as fast as my hot little fingers could dial the phone. If I only could get $400 for the arm, I would skimp on lunch for a while and order an OL Silver anyway. If I couldn't get $400 for the arm, I'd mod it with whichever brand mods I liked best, in the order I mentioned above. Either that, or order an already completely modded OL or Expressimo RB250, by adding whatever I could get from the RB600 and cash difference.
Then when you get this done, you have to seriously start looking at turntables, as the next step. Any of these arms are beyond the P25. Not that they wouldn't be good on it, but they would be far more forthcoming with their possibilites of performance on a more high end table. I'm sure you know that I recommend Teres as the best TT for the least money. I have a Teres 245 with OL Silver, and it is a sweetheart! I'd seriously recommend looking in that direction.
