Springbok10, I do not have all the history at my fingertips but it took a long time for home audio to adopt what the pro world (of necessity due to long cable runs) had used for years. The longstanding prevalence of single ended connection probably had somthing to do with the dominance of a few manufacturers (RCA? connectors) in the early home entertainment industry of the 50's.
The market for phono equipment dropped off drastically after the introduction of CD's in the early eighties. Many of the turntables of that time even came with hardwired RCA phono cables installed! All this was a good 10+ years before the home audio industry began offering balanced connections -- at first just on the better brands like Audio Research, Mark Levinson, etc.
Nobody was really paying much attention to developing new and better phono preamps until (relatively) recently. And let's face it, it's a small market at best. That means that a.) the prices are going to be disproportionately high due to so few units sold, and b.) manufacturers want to capture the largest number of potential customers in that already small market. Since most of the market (still) owns single ended equipment, the designs being produced are largely single ended. But I see that beginning to change.
As for the ones you mention, I honestly don't remember. I'm pretty sure the Manley does, but what you mainly get for all that extra money is a versatility that you probably won't require, since you're only going to be using one cartridge (I presume?) I'm certain the Audio Research phono preamp offers balanced ins and outs (and don't discount that one, it's supposedly pretty terrific -- but that's just what I read, I haven't heard their latest).
If I didn't have my beloved ML 25S, I might consider a tube unit for my all SS system. In your case, as I mentioned earlier, I think a great SS unit (like the TE Groove+) would compliment your system beautifully. Additionally, it could be left running all the time, which for that kind of device guarantees performance stability. Of course, you could leave a tube phono preamp on 24/7 but you don't need that!
The Whest has gotten great press, but like new computer software, I won't buy an audio component until it's been in the market a couple of years. (No beta-testing for me!) I'm also no fan of the battery powered units. Not because they're battery powered -- that's a great idea -- but rather because the production cost savings gained by the elimination of the power supply have apparently not (yet) gone into making a top notch battery powered phono preamp, if you get my drift . . . . . . . . . . .
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