Being that I just went through the exact same process of finding a replacement for my LS2B, I thoght I'd chime in with my two cents worth.
I understand that the LS5 smokes the LS2, the latest versions in particular but as I have no personal auditioning time with this unit I can't confirm or deny this. Also, as you've noted, the LS5 has no single ended in/outputs and few people own completely balanced set-ups. Word has it that the fixes for the lack of s/e ins/outs, ARC's BL units or adapter plugs, are not stisfactory sonically. However, someone who's ears I trust said that run in proper balanced in/out configuration the 5 was superior to both the Ref 1 and first iteration of the 25.
On to what I have heard- A few days spent with an LS16 in the system were completely uninspiring. Despite its true balanced nature it was far noisier and much more vague sounding than the "faux" balanced LS2B. Tube swaps to low-noise-tested premium Amperex, Telefunken, and Mullard tubes did not help. This performance was flat out embarassing, particularly when compared to...
The Sonic Frontiers Line 3SE I'd had on loan for a month. 10 6DJ8 tubes and this thing was dead quiet. We are talking like transistor quiet. Wow! Great, grain free, and smooth sounding with big effortless dynamics and "stygian" bass. This thing had about a million in/outputs, a great remote, a headphone jack (!) and it visually matched my SFD 2 Dac. A shoe-in right? Almost...
You see I'd recently replaced my ARC PH3 with an Aesthetix Io phono stage and this thing is astounding. I currently have the best vinyl playback I've ever heard. After spending some time correseponding with a few other Audiogoners I decided to hang it out a bit and scored a demo of the matching Calisto linestage from Aesthetix. This was a tough call. I have a great local dealer who is absolutely honest and treats me very well but nobody in Canada even brings these things in. I figured if it didn't float my boat I could probably flip it for about what I paid. Well the Callisto is stayin' baby! Yeah I give up my remote and the headphone jack and its a bit noisier than the Line3 (about the same as the LS2B) but it has plenty of XLR and RCA ins n' outs, all implemented properly in a true balanced circuit and it superimposes the performance on my room like nothin' else I've heard. It has ridiculous number of tubes as well so like the Line3 it runs pretty warm but what the hell. If its in your snack bracket, check it out!
FYI rest of the system:
Oracle Dephi V/ SME V/ Benz Ref
EAD T8000 Transport/ Sonic Frontiers SFD2 series3
Aesthetix Io and Callisto
ARC Classic 150s (recently updated/modded)
Merlin VSM Milleniums
2 Paradigm Servo 15s/ X30s
Cardas Gold Ref wires throughout
XLO Signature AES/ABU digital link.
Everything lives on Black Diamond cones/pucks, sandboxes, and Target stands in that order.
The Merlins are run full-range and the subs are crossed in (REL style) to pick things up at about 35hz where the Bam equipped VSMs roll out. I found that a very wierd asymetrical location of the subs along with judicious tweaking of the pair of X30s respective phase controls has tied the subs into the system very smoothly.
Oh, and it all lives in a purpose-built room with DIY tubetraps, wall and ceiling hung abfusors.
