Upgrade my HiFi setup!

Definitely hear a difference. Am an admitted fanboy of InnuOs. 
Also these can have a huge impact, using the pairing tool helps. 

https://rel.net/pages/speaker-pairings

2 suggestions.

1) Wavetouch modded Assemblage ST-40 tube amp + WT WT-95 SACD, CD, flac player + streamer Click here to hear it. 

2) Bluesound powernode modded.   Click here to hear it. 

The room in videos is 32ft W x 44ft L x 12ft H. You won't never envy of $million system with these humble systems. They are very affordable. 

Alex/Wavetouch audio

I used to have the LS50’s in a room the same size as yours, they are a great speaker. It is challenging to find replacement that is that good and also won’t overpower the room. I was successful in adding a subwoofer to that system and had fairly well balanced sound.

The Rega is woefully underpowered for those speakers, especially given your preferred genres. I would keep the speakers for now, add a subwoofer, I had a REL 7i, and consider an amplifier upgrade. On top of that get a separate streamer and DAC. All of this you could do for under $10k, especially on the used market, and significantly upgrade your system.

For the record I went from the LS50’s to a used set of KEF Reference One’s. They were a bit much for that room as they need to be out from the wall a bit. If you like the LS50 sound, the Ref’s are just an amazing upgrade.

Personally I think Monitor Audio is highly underrated/undervalued, but I don't think the sound will be the same.  The mid-treble in particular will be different and you should be sure of your choices.