Why are my B&W 803D speaks feel bright

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.

The 803Ds can sound very very good indeed when driven by very good tube amps. I would recommend the best amp and pre-amp you can afford.