After living with MA Silver RS6's for several years I just pulled the trigger on a pair of GS20's. I've always appreciated my 6's for their even balance at low levels and ability to belt our the party music. I'm on my second day with the 20's and here is my immediate impression;
1) Soundstage is much larger and begining to open up even more. Speakers are begining to disappear with good recordings.
2) The highs are very detailed and very seductive. It's obvious that MA used higher quality parts throughout as the 20's sound much more refined than the 6's.
3) The build quality and finish are top shelf. Rock solid cabinet. Make the 6's look like toys!
Keep in mind that they have had maybe 5 hours of break-in. If they end up as seamless as my 6's (which I expect once the base comes around) the 20's will be well worth the 3X price of the Silver SR6. Check stereophile for a great revies on the 6's. The MA website has a glowing review of the GS20's on their Service/Past Product tab.
Would like to finish by saying I think the Silver RS6's are on of the best audio values on the market. I suspect the Silver RX6 to be excellent also despite it's rise in price. But, if you can afford the 20's they are a wonderful indulgence. Highly recommended!
Associated equipment: Mac 6500, Rega P5 w/ Clearaudio Maestro, Creek Destiny CD, Audioquest and Kimber cables/interconnects.