I have owned an LS3, LS7 and now a LS2BR. If you like the LS3, you will LOVE the LS2. It is a long story, but I sold the LS3 to buy the LS7. I was absolutely in love with the tube sound. To me, and for my system, the ARC tube line stage sounded wonderful. The LS3 had excellent dynamics and superb bass control. I tried a friends LS7 and immediately fell in love with the depth of stage and smooth and lifelike sound of it. I bought the LS7 and lived with it for about a year. It used 4 tubes, which isn't to bad, if you start tube rolling (which you should do), but it can get expensive if you start going for some genuine NOS tubes. For the record, I tried the ARC factory tubes, Valvo "red" labels, Amperex Bugle Boys as well as a couple cheap stand bys. The Bugle Boys are the best I have tried. The LS7 lacked a little in the bass, but the focus was good, but not as good as the LS3. However, the overall sound and image was, to me, better than the LS3, it was more 3 dimensional.
On a whim, I bought the LS2BR. Its power supply seems larger and beefier to me (If anyone knows if this is true, please let us know!) and only uses one tube. The balanced output was a bonus, since my active crossover has a balanced input. I wanted the remote as well. This preamp is head and shoulders above the LS7! The pinpoint accuracy of the LS3 was back, and the lifelike stage (3D effect) was there from the LS7. The depth of stage and proper size of the artists and the instruments is much better than the other 2. With only one tube, I have quite a supply of tubes, which will last for a long time and tube rolling is less expensive. It is much more sensitive to different tubes though.
I haven't heard the other pre's you have mentioned, but their reputations are very good. I would recommend without any hesitation, the 3 pre's I have mentioned. But for my system and tastes, the LS2 is the best I have had. If you don't need the balanced feature, you can also save a little money and buy an LS2. You have to make a decision if you want a remote, because that model is usually a little more expensive.
This is a GREAT forum, and you will find a lot of advise, from good people. You can also try Audio Asylum as well, there are a couple of ARC experts (self proclaimed!) and the they are very helpful and knowledgeable. If you have specific questions, just email me! Hope this helps, let us know what you end up doing.
Best regards, Matt