Where should I start upgrading?

@Titus1 - my apologies - I assumed since you had the the Nagoka 110 whose complaince is 6.0 x 10-6 cm/dyne, that the Denon at 5.0 x 10-6cm/dyne would work.

You could try the Denon 301 with Compliance: 13x 10-6cm/dyne or the Dynavector 10x5 with a Compliance 12 x 10-6 cm/dyn

The Grado Sonata has a  compliance of 20 X 10-6 cm/Dyne

Being a big fan of Soundsmith - I would contact them to see which one of their own cartridges is best suited to your arm.

There are lots to choose from ...

Regards - Steve

Thank you for all suggestions.
Randy-11 good idea to have the turntable in another room but unfortunately not for me, the cab length will be overlooked. I have already done room treatments & moving speakers around.

Donvito101 Maybe a subwoofer that is bigger and faster is a good idea to borrow and listen to.

Zavato / williewonka I also think an upgrade cartridge will make the overdue difference since the MP-110 is a cheap product. It works well with a little extra weight on the cartridge shell. Is a bit hesitant about the DENON 103 cartridge as it is made for heavier tonarms

@titus1 - if the Nagoka works with the arm and since you have MC on  your phono stage, I found that a Denon DL 103 cartridge sounded much nicer and more musical with lots of detail

I then moved to a Soundsmith version of the Denon 103 with a ruby cantilever and finer stylus profile - Cost around $650 CDN.

One of the best upgrades I've done

I plays pretty much anything I load onto the turntable without any issues

Regards...

I like it all- perhaps move up the Nagaoka line? 

Looks like it should sound good. What do you want to change in terms of the sound?

It looks like that 8 inch subwoofer might be a weak link in your system. It would be a good start to replace it with a 10 or 12 inch sealed type . Take a look at these!
http://www.jlaudio.com/home-audio-powered-subwoofers-e-sub
http://www.theabsolutesound.com/articles/jl-audio-e-sub-e110-subwoofer/

1. put the turntable in another room for acoustic isolation
2. get the pre- preamp and put it as close to the turntable as possible with a short cable run, then run longer cables to the preamp or receiver
3. room treatments & moving speakers around to optimise the room effects 
4. new speakers