Why are my B&W 803D speaks feel bright

The only way to properly determine the exact cause of your issue is through experimentation. But good insight before you do never hurts.

Most of the B&W speakers I had an opportunity to listen were forward in their presentation. I fortunately have heard the 803D and 802D. They were not in the same system so I can not provide a proper comparison between the two. My impression didn't have any notion of brightness, but its presentation has a forward presence that might not mate well with some components (particularly ones that have been described in a similar way). I have heard people using Classe with excellent results and my best experience with them was paired with Naim. Another setup I heard with the 803D was surprisingly lifeless. I had forgotten what the rig was, mostly because it didn't really leave great impression.

BTW, could you provide a more detailed description of the room and speaker setup. It could greatly affect the bass performance and thus make the balance all wrong. With a speaker such as yours, system synergy and setup are two very big factors. I personally have not heard any of your gear in any system so I can not comment on them.

Almost any speaker can be made to sound good or bad depending on set up.

I own B&W802D and listen bazzilion time 803. Absolutely not bright speakers (not mushy with diamond tweeter too!). Very, very accurate - they reproduce exactly what you send to them.

To begin with while meridian is very good amplifier it cannot drive such strongly reactive load as latest B&W are. Unless you change your amplifier to more powerful (yet very musical) there is nothing to talk about. For reference only I use Spectron Musician amplifier

Now, then electrically you are OK, lets look onto sound. I never used DVD as the music source so I cannot comment here

Preamp. May be its personal bias but I always consider Rotel as a cheaply sounding, cheap amplification and not on the level with B&W (just B&W Group owns Rotel, Classe and I believe McIntosh - so these amps are mostly used with B&W). I like and use only tube preamplifiers so my advise is to get one (good only). Again for reference, I use Joule-Electra preamp.

All The Best

Actually I recently heard a pair of previous generation [ 5 years old or so] 803s driven by a Rotel amp and pre and they were far from bright. Possible the new tweeter would make a big difference but these were in a very reflective room. Rotel makes some quite good equipment at the top of its line, I would rather have their top equipment than Mac SS or any Class D amp. My Meridian amps drove my Apogee Duetta Signatures with no problems; they have trouble with my GamuT L5s, which go down to 2.8 ohms. Driving them hard for long periods will cause them to overheat but the sound is very good. The Revelator tweeter in the L5s supposedly go out to 60 Khz [ I cannot confirm this personally and the bats of my acquaintance have refused to comment] so they do not lack high end. You may just not like the new hard dome tweeters, I do not care for the ones I have heard myself. It is a matter of taste, they are technically very good. In the distant past I used Ionic tweeters, which achieved a similar degree of technical perfection but sounded quite different. As a matter of fact, B&Ws first speaker, the P2H, used the Ionic tweeter, so they have come full circle. I had a pair myself in the late 60s.

You would rather have a rotel ss over a set of Mac501s or even the 402 on the 803ds? Having owned and heard both on this speaker there is no comparison...at least to my ears.