Tube pre-amps: balanced a big deal?

You won't really lose anything. The soundstage that opened up was due to balanced being 6db louder than single ended, you'd just have to turn the single ended preamp louder to match. We perceive louder as better, always.

Balanced is great for long, long runs, otherwise for typical in home usage you wont notice anything else besides the free 6db gain. 

I had the DeHavilland Ultraverve, it's fantastic.

Not sure if they are balanced, but CAT are among my favorites.

I try to keep things simple;
A phono cartridge is a true balanced source. The sinusoidal waveform goes up, and then it goes down. A dual differential phono pre amp, pre amp combination preserves the entire waveform. An asymmetrical (rca) pre amp references the negative (down) portion of the waveform to ground. It's a little forward to say it's thrown in the garbage. However, with careful manipulation of negative feedback, a single ended pre will restore some of the negative portion.

Once you start down the balanced path, you need to go all the way. In time, and as funds allow, you will have a fully balanced system from diamond tip to amplifier output.

Here's where the problem starts. Most speakers have asymmetrical crossovers. If possible, try to find Gauder Acustik speakers. They use a symmetrical parallel crossover. When driven by a fully balanced signal, they are truly remarkable. Salk Sound uses an almost symmetrical series crossover. If you do a search, you'll hear a recurring theme; people that own Salk speakers, rarely change.

Thanks cousinbillyl, good insight.

Even better is no crossover at all. The Eminent Technology LFT-8b uses two paralleled push-pull magnetic-planar drivers for the 180Hz-10kHz range---no crossover!