Off Tracking the thread more and on Webers, the Weber I feel are really better than PMO's. The Italian Webers are better than the Spain or US version. And I see now that China is making a weber copy in the IDF series and Frankly I would not even try it.
46's have gone down in price recently and there was a set unsold for $4K ,
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/972527-46mm-weber-carbs-sale.html
I sold a set of Italian 46's for $5,000 just last year, so that surprises me on this nice set is unsold at $4K today.
IDS Weber are worth money to the S crowed, about 5-6K like Matt states, but should not be any more valuable to any one else because they were a 'band aid' fix to the high compression 2.0 S motor that really needed twin plugging on those head shape. The 40 IDA is better for power and performance, that is why Porsche raced with the IDA's and not the IDS.
IDA's go for around 2-3k depending on linkage and shape.