Keep the Mahlers. I had (have)the VA Bachs for 3 years and upgraded to the VSA 4jrs almost a year ago. My comparisons are based on these two speakers and have spent a great deal of time listening to the VA line up through the Beethovan's. I've never heard the Mahler's but, I bet they are glorious sounding. So keep those comments in mind when disecting my thoughts. I found the VA speakers to be extremely listenable, probably due to the silk tweeter. My wife and I could listen for hours. Ultimately, I upgraded because they just couldn't hang on loud R&R music. I'm very happy with my 4's and they keep getting better and better as my system evolves. BUT they are more neutral/cleaner sounding to my ears than the Bach's. I don't want to give the impression that I'm not a fan of my 4 jr's, because I am. It did take a while to adjust to the difference in sound between the two lines. I still have my Bach's and will take them out of the attic some day to build another system. I guess what I'm getting to in a round about way is, I think at best you will be making a lateral move and may or may not like the sound better than what you already have. FWIW if I ever get rid of my 4 jrs' the Mahlers would be right at the top of the audition list.
Good luck.
Good luck.