I never received any responses to my post but I did get very good tips on other forums and thought I would update for the benefit of those who use the REL sub bass systems.
I spent almost 6 hours listening to music and tweaking the system on Sunday. I got some excellent tips from fellow members on the LS3/5a club, of which I am a member. One of the guys was quoting about his discussion with Richard Lord who said that most of the audiphiles make the mistake of setting the crossover point too high and gain too low which actually does not help the overall balance. In my case, I had set it at 28 and gain between 10 and 11 o'clock, so to a great extent it is not incorrect. Anyway, listening session on Sunday was very useful as I managed to bring the crossover point even lower at 25 and increased the gain to 12 o'clock. I did not notice anything wrong with the system or its overall balance. In fact the system was sounding much smoother at this point. So I will not touch it for next few days and continue to listen and evaluate various albums.
The other interesting point that was informed to me on the club is that according to Richard Lord, setting between A1 and A3 is somehow workable with all speakers no matter what their frequency extension. I was surprised to find this out but realised that somehow folks at REL know what they are talking about. I did set it on this position and the system is sounding wonderful with great extension and depth, without my missing anything in between whatsoever. The most surprising disclosure was that REL themselves tested the LS3/5a's and they used the same low setting and higher gain and according to them its was subjectively very good integration. Do not ask me to explain this as I have no clue whatsoever how it is achieved but that is the exact setting I used for the Chartwell also, it was surely sounding great.
Any REL owners wish to share their experience on this thread?