Typical upgrade path from VPI?

I've had my Scoutmaster w/Sig arm for a couple months. It came with a Shelter 501 MkII cartridge setup by Elusive Disc. I've since had it re-setup and between that and break in, it improved.

I've recently added a 3g headshell weight (as per suggestions). Unfortunately, my main complaint still lingers: lack of midbass. I can switch to a CD (Benchmark DAC among others) and midbass seems fine, but absent on the TT. I get LOW bass (if there's low bass on the recording, I hear it as if I have a subwoofer), but mid-upper bass is weak.

It could be the Shelter, I realize this. I am willing to try another cartridge, and in searching threads on this, I read a lot of comments suggesting that the JMW tonearm (even sig version) is only so good (i.e. don't buy an expensive cartridge).

If one wants to bring things to the next level, are there compatible tone-arms? I also read complaints about the pivot tech of VPI, which suggests another TT may be something to consider.

So I'm curious as to what other brands of TT I should consider.

My system:
Rhea Signature phono
ARC Ref 3 preamp
Theta Citadel 1.5 amps
Speakers are still being auditioned (Dynaudio, Rockport in the running).

Thanks