sony x707es questions

I have a x707es player and would like to better it. From what I've read it is a decent player. My options would be
1- sell and upgrade alltogether? probably coslty.
2-use as transport only and get a dac, I could use some advice on what dac would pair well with the sony and be an improvement over the onboard dac. Would need to find dac with volume control as I run direct to welbone labs drd300b amps
3-mod the cdp as well as run dac, this would probably be the ultimate for this particular player as far as improvement. I have contacted APL they will not mod my machine at the moment they are to busy, so this may not actually be an option.
Any insight/info would be appreciated Tahnx
My suggestions:

Forget APL and contact RAM. All these questions would be best answered by RAM. These type of questions are at the heart of their business.

Also, I would scrap the "free lunch" volume control option you've chosen and do it right with a Placette RVC. The improvement would be HUGE.

Happy Listening is supposed to be the best. And the only one Sony endorses. Shipping is the only drawback unless you are in Europe. I have a 707 myself and it makes an excellent transport and sounds better on it's own than many newer models.