MC300 MC252 MC501 recommendations based on my setup

So I have 2 systems, 1 downstairs that runs the whole house (4 sets of speakers on a switch) with a C48 and MC252 and Paradigm Signature S8's as the mains in the primary listening area. 
I also have a medium size room (large for a house) with a C40 and MC300 on Polk Rti A9's that are just a place holder until I can find the real speakers that I want (Thinking B&W 800 series).  

I like to listen to my music very loud and like to "feel" the music but the MC300 is not cutting it with either set of speakers.  

I have an opportunity to get a set of MC501's and would really like to see what the suggestions would be for a set of speakers that would pair well with them also considering I can move any of the other components upstairs or down stairs to get the best setup in both areas. 
Do I buy another  MC252 and bridge them or biamp them?  Is the MC501 investment worth the upgrade assuming the addition of B&W 800D's later?  How much are the MC501's worth in good shape? 

I have a lot to consider because I am also thinking about upgrading preamps also (interested in a tube pre C2300 or 2500 based on past experience w/ a Vincent MK236) but mainly listen to SACD's in one area and a combination of vinyl and SACD's the other.  (BTW, I also have an NAD M51 DAC that I really like upstairs with the C40)
I run a Mac C2500 into a MC452 to drive a pair of JBL 4367s. The system is very dynamic and clear, no strain at insanely high SPLs. I like it loud also. 
Man I would love a set of 4367's but they are just out of my price range and I actually may not have the room for them anyway (I would have to measure).  I need a little bit smaller footprint I believe.  I sold a set of JBL's (strangely, I cannot remember the model) in 2005 cheap that I am totally kicking myself for getting rid of to this day. 

BTW, do any of the newer tube pre's have an eq built in? 
I replaced my MC352 with the 501's and never looked back.
They first powered Von Schweikert VR4HSE's and now power
Innersound Eros with Sanders new electrostat panels, and I love the amps.
The first diff I noticed was the low end impact, it was almost as if I added a sub because it seemed to really grab hold of the woofers on the Von's.
I don't think you can make a mistake upgrading and prices are really
good because lots of people went to the 601 or 611's.
@gene3x I don’t think any of the tubed mac preamps have the EQ that some of the solid state preamps have, but I could be wrong. My C2500 has bass and treble tone controls and they work ok. 
My room is 17 x 21 and the JBL 4367s sound great. I’ve seen these speakers used for <$10K