However, if you simply want the ability to play discs, which is understandable, then something like the Marantz wouldn't be stupid money. A second hand Marantz should be very easy to find for little money and won't bring the Rega price.

It's a good player, but it has its own character, as does the Rega. The Rega is well composed and dimensional if a bit safe sounding. The 6005 is a bit lean on the bottom and less full sounding than the Rega, but more energetic with decent PRAT and a more extended top end, but not to the point of being ragged.

If your ribbon tweeters are too dry or harsh, go with the Rega. If your system needs a little injection of PRAT, go with the Marantz, though I doubt you will be blown away by either player or feel that your money was very well spent. Neither player betters their previous models, though the new Marantz sound is a considerable deviation from their previous issues.

Most people that aren't very fond of digital to begin with would appreciate how Rega sounds and Marantz appeals to people who can deal with a little impoliteness in punching above their weight, if that makes any sense.

I have no experience with the BDP-450, but I will guarantee that the analog outputs of a OPPO 95 or 105 will give better sound quality than the HDMI outputs of the 450.

Having said that, however, the VERY weak part of your system is the LX57!

It has Class D amplifiers and the sound quality is simply not up to audiophile standards; very mediocre. That will stand in the way of getting good sound quality until it is replaced with a high quality unit.

You definitely should be looking at a new receiver/ amplifier FIRST. That is where a major improvement in sound quality is going to need to happen.

You say nothing about the speakers being used, or how many channels are involved. Only with that information in mind, and a price range, can one recommend any specific equipment.

Cambridge and NAD are the best-sounding HT receivers IMO, and for
2-channel integrated amplifiers, Musical Fidelity, Creek, Arcam and Rega have good-sounding amplifiers available.

A good amplifier will transform the sound of your system.

XXX

Since the 450 also has a digital coax out, why not just buy a better D/A converter? For $600 there are plenty of good quality units around.

If you own a number of disks or just like spinning CDs then get yourself a dedicated player. I just picked up a used Cary Audio 306/200 and it's a marvelous "older" mature machine. I love it!

Keep spinning those CDs!