Next Upgrade?


I like my system, but sometimes feel it sounds a little muddled. Jazz and standard rock are pretty good, but harder rock/metal can overwhelm. I just know I could improve, and thus the obsession begins. Peachtree Nova 150
Kef LS50s
Rel T7i sub
Ortofon 2M Blue
Technics 1200 M3D circa 2004
using the built in stage on the Peachtree
stock power cables
Audioquest Golden Gate inters and Rocket 11 speaker cables. 
I feel like TT and or cartridge would be next move. Room is like 14x18. I’ve tweaked about everything ie speaker placement, footers and isolation.  Treatments out due to room and wife. I have a Thorens MM008 stage but I didn’t think it was any better than the built in. What’s the weakest link?
ronribbons
When hard rock on louder volume starts sounded distorted it's most likely an issue with your self-described lack of room treatments. The problem becomes 2nd reflections which are muddying up the room sonics.  I don't see how you're going to fix this issue with a gear change. Even some bare minimum diffusion/absorption treatments that tick the "manageable aesthetic" box with your room and wife would be worthwhile to explore.
If you want to play loud music effortlessly you need a 2nd sub and an active 2 way crossover. Cross at 100 Hz. This will unload the LS50s increasing your headroom 3-6 dB and add more solid bass which will give you the impression of more volume. The changes you are talking about will not head you in the direction you want to go in.
If you want to play loud music effortlessly you need a 2nd sub and an active 2 way crossover. Cross at 100 Hz. 
 
How would one do this using an integrated amp?  I have been looking at this today and can't find a way without separate amps - preamp.
ls50’s showing strain at higher volumes or the peachtree is not up to it (more likely the former)

if it were me i would find larger, more efficient speakers that play loud with more ease