I purchased the SONY SCD 555 ES about a year and a half ago. I needed a new CDP and I was intrigued by the potential of SACD ... also, the price for the unit, at the time, was good (40% off list), and I figured what the hell. I have the SONY hooked up as a 2 channel player in an audio only system. I have since purchased about 35 SACD titles, of which about half are hybrids. I am happy with the SONY and SACD, but I am fairly certain that I would have been just as happy with redbook CD playback on a good quality CD player. As for DVD-A, I felt that any DVD-A worth owning would sound fine on my DVD-V player (which is part of a 2 channel HT set-up; with a Pioneer PD 65 used for CD playback).
At the end of the day, the quality of recordings is the real culprit. I am finding that the better the equipment is, the better the quality of the recording has to be, as the equipment is more unforgiving of mediocre recordings. So, when given a choice, I will purchase an audiophile pressing (XRCD, etc.). BTW, I find HDCD's excellent ... they sound great on my 3rd CD player, a Music Hall CD 25.
There is also the new format software environment to consider (limited number of new format releases, the new format version of a new CD release that you want may just never happen, and you will inevitably wind up buying your new format discs mail order).
If you attempt to cover both formats, you will have double the frustration. Unless you really must have surround sound audio ... you must just wish to pass on SACD/DVD-A. If I had to do it all over again, I would probably have gone for a good quality CD player (like a Rega; MF; etc). SACD title chasing is frustrating and the Record/CD Companies do not make it easy. Fortunately, the SONY is worth owning and I stayed way from DVD-A.