I have had my new to me MC A90 in the system for almost two weeks now and I am very impressed! I set the Whest up at 100 ohms loading with 65 db gain. After reading an article by Fremer on using his A90 with a new PS Audio phono stage, he set the loading at 200 ohms and preferred it. I have a 220 ohm setting in the PS.30 RDT SE, so I decided to give it a try. I must say the results are interesting. I cannot say yet if I prefer it over 100 ohm, but it does seem to bring out the mid range and upper end with more detail. I plan on running this for a few days before swapping it back to 100 ohms just so that my ears acclimate.
As far as using this high end MC vs. my AT20ss MM, I can say that it definitely has more to offer in all respects; however the AT20ss is no slouch. This is not like a holy moly moment; it more like now that is very nice. It should be as it's nearly a $5K cartridge vs. a $250 cartridge (in 1976 dollars which might be equal to around $1800 today). For a guy on a tight budget, he'd serve himself very well if he could find a good like new AT20ss out there; it's 90% of the MC A90. I like what qdrone suggested, go for the high end MC. To gain 10% more in performance in a high end system is difficult to achieve and by simply adding in the A90, I seem to have done this.
As far as using this high end MC vs. my AT20ss MM, I can say that it definitely has more to offer in all respects; however the AT20ss is no slouch. This is not like a holy moly moment; it more like now that is very nice. It should be as it's nearly a $5K cartridge vs. a $250 cartridge (in 1976 dollars which might be equal to around $1800 today). For a guy on a tight budget, he'd serve himself very well if he could find a good like new AT20ss out there; it's 90% of the MC A90. I like what qdrone suggested, go for the high end MC. To gain 10% more in performance in a high end system is difficult to achieve and by simply adding in the A90, I seem to have done this.