I wonder how does it compare to HD 598. I am new to audiophile, and only have HD 598 for a couple of months and I loved it. Just wondering how different is the HD5x9 vs HD5x8
Based on what you described, I think you'd have a hard time telling the difference. Honestly, I think a lot of experienced audiophiles would too, in a blind test. These are great headphones, for sure, but since you have 598s, I'd say spend your $$ on a different sounding headphone or a different type (like iems) to help you get a sense of the different sounds that headphones can deliver. Lots of good ones to choose from around here, and you'll have no problems getting recommendations from the folks around here if you tell them what you're looking for.
Yeah I agree with GunsOfBrixton. If you have the 598s these genuinely might be a bit redundant. They are very similar. Save you money for something else. No point in having 2 pairs of headphones that are so close in sound signature and quality.
Too bad you missed out on the Beyerdynamic 880/990headphones that dropped recently they have a very different Sound signature and well worth it. Also look at AKG they are a top seller.