Upgrade phono stage?

I am looking to make and upgrade an I think the weakest link is my phono stage. I listen mosly to blues, then rock, folk, jazz. The Zphono is not bad but i would like to get a bit more out of vinyl. Thanks.

My system is:
Primaluna PL2 w/kt88
Pro-ject Xpressions TT v1
Parasound Zphono
Triangle Comete es
Ortophon Super OM20
Shure V15VxMR stylus bent
Grado Gold love the sound

I have a budget of about $500 for used gear.
This is what I have been looking at but im open to any and all suggestions in my price range.. I am open on tube or SS. I would prefer mm/mc with adjustments as I would like to try a MC cart sometime.

Pro-ject Tube Box SE
Graham Slee
Jolida JD9a
Dynavector P-75
Wright WPP200C
go with the wright, sweet sound, good value in the used market but plan on replacing the tubes.
the grado gold is solid, but an at150 will be a dramatic improvement...less than 300 bucks
I suspect your cartridges are the weak link. I haven't heard the Grado Gold, but if you are in love with the Grado sound, I had a Sonata, which was pretty good and would fit in your budget - you might even do better and get a used Master. I upgraded to the Statement Reference, which, even at $1200, was referred to as a "budget cartridge", which may help put your Gold in perspective.
to hear a big improvent over your z phono you will have to spend more than 5oo