Burr-Brown PCM63 vs 1732

Just acquired a Onix XCD-88 with a (single I believe) 24bit onboard DAC. Would an Adcom GDA-600 (ca 1993; with dual 20bit PCM63) be a step up?
Spring for the new Sony XA5400ES with a street price of $1100 and you will be state of the art for years to come:O)
Onix is a cloned Music Hall CDP and has recieved many accolades on agon over the years. If you decide to keep the Onix you may want to upgrade the op-amps to 627's. Will need to mount them to brown dog adaptors. They're a fairly inexpensive upgrade that pays for itself in performance. The 627's pull great amounts of detail from the discs. The Onix also casts a very wide soundstage. It's not a bass monster. It also decodes HDCD, you may have hdcd discs that you don't realize you own until the Onix tells you. A nice feature. At its agon price point, the Onix is a really nice piece to enjoy on your way to a higher performance machine such as recommended by Dave b.
Thank you for your responses. Yes, I'm planning on the opamp upgrade. But, I'm hoping someone has an opinion as to whether an old (ca 1993) adcom external DAC with 2 20bit burr-brown PCM63 would be an improvement over the single burr-brown 24bit 1732 onboard the onix. Thank you.
I'm a big fan of the Adcom GDA 600/700 DACs: I own the 700 and am constantly amazed at how well it stands up to newer, pricer models. I really don't think you can go wrong with a GDA 600 since the cost of picking one up is only a few hundred dollars; cheap! They are VERY WELL BUILT! and simply aren't given the credit they deserve. My 700 is built like a tank and sits next to a YBA CD and and a North Star 192 DAC. And it can hold its own...
I've heard some people say they like the 600 better, but either one would be worth a listen.
The McCormack DAC is really good too.