I remember the Syrinx PU-2 as being pretty "tweaky" and difficult to set up. As a fellow owner of the Rega RB-900, I can't see any point in replacing it with the PU-2. The RB-900 features a 1-piece casting and very closely "spec'd" bearings, and Rega has said in various articles that the tonearm's price is about half what it would be if the same casting process were developed today. In short, the RB-900 continues to be a significant "bargain" among high-end tonearms. If I were going to replace my RB-900, my "short list" would include the VPI JMW-10.5 or JMW-12.5, and the Graham 2.2.
For other thoughts about the Syrinx PU-2, click on the following two links:
1. http://www.hi-fiworld.co.uk/hfw/oldeworldehtml/syrinxarm.html
2. http://stereophile.com/tonearms/821/index5.html (note the comments at the bottom of the article about Syrinx and the quality of the bearings compared to the Regas).
For other thoughts about the Syrinx PU-2, click on the following two links:
1. http://www.hi-fiworld.co.uk/hfw/oldeworldehtml/syrinxarm.html
2. http://stereophile.com/tonearms/821/index5.html (note the comments at the bottom of the article about Syrinx and the quality of the bearings compared to the Regas).