Sure. You can always benefit from spending money!

But whether it is the best way to spend your money, I can't really say, never having heard the Yamaha.

Others will probably violently disagree, but unless the Yamaha converters are gawd-awful, there might be other things that would give you just as much or even a more noticeable improvement in your recordings - like a better mic, better preamp, better outboard processors and effects, better monitors, or better room acoustics.

If you've dealt with all of those things and you are happy with the Yamaha otherwise, then sure, go for the converters. I'm not minimizing their importance, but just saying in general it's not the very first thing I'd look to upgrade.

(Recently I had a chance to hear a comparison of a Pro Tools HD mix going direct to powered monitors through its own D/A converters versus taking a digital output from PTHD into a Benchmark DAC-1. There was definitely a noticeable tightening and increased clarity in the bass frequencies using the DAC-1. So please understand I'm not dissing good converters! Especially if the ones you are using now are particularly crappy.)

Great converters can always make a big difference. But the differences or benefits in any gear is more related to your ability to be able to hear those differences and benefits. The weakest link in the chain theory applies here. If your signal and monitoring chain is not able to provide the necessary detail for you to hear the improvement, you will not be able to clearly notice the differences or benefits. And what differences or benefits that you do hear may not be really true to their nature.