Well I eventually carried out the horn and high frequency driver modification to my RF-5's and replaced them with new ones out of the RF-7. I purched the parts direct from Klipsch, having failed by obtain them second hand.
It must be almost a year since I carried out the modification (it's taken that long to get back on here - password and login probs!), I can confirm that I am very satisfied with the modification and I will not be changing back!
To give a review, I need to put the modification in perspective, I live in the UK where Klipsch is not easy to come by, so simply upgrading to RF'7's is not a viable option due to the high import duty and postage costs. I first heard Klipsch La Scala's at my school in Hong Kong and became influenced by the Klipsch sound from a relitively early age. Recalling the Klipsch sound from my early years, I imported the RF-5's about 7 years ago. About 5 years ago, after reading Dean G's threads, I upgraded the crossover networks using Kimber capacitors, this improved the speakers significantly by giving far superior deep and crisp base and improved clarity all round.
I always thought that the HF drivers were the weak point of the RF-5's as I was able to hear very clearly the superior smooth sound that came from the RC-7 centre speaker. When I eventually changed over to the RF-7 HF drivers, the mid and high frequency sound was so much more smooth and the soundstage across the front three speakers was far wider and matched giving a more realistic impression when watching concert DVD's or Blu Ray's. In the beginning, although the modification was obviously an improvement, the improved efficiency of the HF drivers resulted in the midrange being slightly overpowered, I resolved this by lowering the 5000Hz band on the room equalisation of my Tag Mclaren processor.
I have to say that replacing the HF driver without first upgrading the crossover caps and without having the facility to alter the frequency output would result in a speaker which is very prominent in midrange frequencies due to the higher sensitivity of the RF-7 driver. However, with the modifications I have done, I am extremeny pleased with the result.
Happy Modifying,
Callum.