Should I switch to a preamp with balanced outputs

I would stay with the equipment you have because you like the sound and thats the most important factor as far as I'm concern. You don't have to spend a fricking fortune to create great sound.
Over 30+ years I have experimented with single ended vs. balanced and in my opinion unless tou have a really long run for your interconnects you are fine with single ended. I agree with Brauser's comment.

I have a new preamp, VTL 7.5iii, with balanced and RCA options. I switched to balanced because the mfr prefers it. I cannot say I notice any improvement, to be candid.

BTW, I have a Belles 150A Hot Rod in my 2d system and I LOVE that amp. Paired with a CJ PF-R SS preamp (top of the line, its time) and I am very happy.

The reason why I originally went balanced way back "when" was because I saw that I could get 'better' interconnects at a lower cost if I went with balanced. (Pro Audio Gear). I ended up staying with balanced. The old addage is that balanced cables fare better on long runs, but thats from the live music where youre running cables from trailers over 50 meters, etc., and my understanding is that some of those uber long runs had some sort of voltage line amps or repeaters of some sort. In any event, to continue, just because your gear has a balanced conector doesn't necessarilly mean that the circuit is a balanced desgin and takes advantage of that design. Some balanced connections are only to facilitate connection and do not implement a balanced design.

Some manufacturers put balanced connections on their equipment to advance their "higher quality" aspects of the piece. There are many XLR equipped components that aren't really differentially balanced...have two complete circuits one each for the + portion, and one for the - side. I have Ayre components that does do this... and using balanced operation sounds way better than single ended.

SE versus balanced is largely a matter of taste and layout. If you have long cables from amp to pre-amp, you're probably better off using balanced. If not, SE works fine. For me, SE sounds consistently better--more liquid and dimensional; balanced sounds more detailed and articulated but flatter and less engaging. This is ture for me over a variety of very good amps using a fully balanced pre-amp. Maybe a different pre-amp (mine's a VAC) would tilt the balance toward balanced, as it were, I don't know. I have identical sets of cables terminated RCA and XLR, and I keep trying balanced but always go back to SE. That's just me. Others consistently prefer the opposite.