Well, it depends. With the R1 I got a very nice sound with a weighty low end. Not bass boosted per se, but the bass had some serious muscle behind it. Soundstage wise it was lke being in the first row at a smaller venue. The Quickstep, on the other hand, had less muscle behind the bass but the soundstage and separation was better. Like sitting 2-3 rows from the stage in a larger venue, giving you a better overview of everything, allowing you to accurately place the sounds.
The PB2's single ended output was much like the sound of the Quickstep, but with the soundstage of the R1. Balanced output, however, is great. I get the muscle of the R1 (even on low gain...) with an amazing soundscape. Soundscape, not soundstage, because things are now happening around me, not just in front of me, like I'm on the stage with the band. Everything has it's clear place in all directions (on good recordings) making it easier to pick up details since the sounds aren't falling over eachother to get to your ears.
The gains depend on the rest of your chain. With well-made recordings and my highly resolving ciems (that were already doing VERY well in the soundstage department), the gains are worth the trouble. I also recently picked up a used set of HD595's for use at home and reterminated them to 4-pin mini-xlr:
Then I just use whatever adapter I need, Hirose or 3.5mm, depending on what I use them with. The 595 is a nice and comfortable headphone, but the gains from going balanced are less than they are with my ciems. I actually find the R1 amp to be the most enjoyable pairing with them.
Conclusion: With good source material, a good source and resolving headphones, going balanced is worth it (to my ears).
Keep in mind that I solder all my own cables so I only have to worry about the cost of the parts - $10 Hirose connectors, $4 Mini-Xlr...
