There's no doubt that the Cary 303 is a very good player and now that the 303/200 is out, you should be able to find a used 303/100 at a reasonable price (since NEW 303/200's can be had for less than $2K discounted).
Just my opinion but... I doubt you will ever recover your investment in modifying gear vs. a popular piece of unmodified gear (like a used Cary 303 or similar popular item).
Just my opinion (again): If SACD is *that* good, a cheap SACD player should sound pretty decent playing SACD media. With SACD players plumeting in price, I would opt for a high quality redbook only player and get a cheap to modest SACD player if you still need to play SACD media. That is my strategy anyway... Will wait a bit longer before buying my cheapo SACD unit. In the mean time I'm enjoying my Cary 306/200 with my huge redbook CD collection.