If I had a 20 million pound budget to make my perfect garage my ST would be there but i don't think an RS would. I mean they look great and they are a nice drive but if you're not an RS enthusiast, and you already have an ST, then IMO it's almost a waste of £30,000 (i know i just lost a lot of friends saying that, lol!!).
If you've already got an ST, get Mountune/Wolf/DS with a set of springs and dampers, maybe upgrade the brakes then you are well on your way to being as quick as an RS and in some situations you will be quicker.
So what i'm saying is, if you love RS's then get the new RS. However, if you love a fast ford, get a tuned ST3 + buy a classic Fiesta XR2 and still have at least £5000 change left over, and thats if you buy the ST brand new!!!
My ST cost me £12,500, the Mountune kit with the exhaust cost a total of £1500 fitted and the Eibach pro's were £400 fitted. Now she's not quite finished but thats £14,400.
I would get £11,000 if I sold it so that's an extra £19.000 i would have to find from somewhere, and that's an awful lot of money to replace one fast Ford Focus with another fast Ford Focus.