A friend went from Gyrodec to SME 20/2 with SME V and never looked back. I went from Gyrodec with SME IV(special build) which was virtually a V without VTF spring adjustment to Gorbe (Gyrodec with Orbe platter, better PSU, chassis upgrade kit), then added Pete's pylons and designed my own feet, all of which made it sound better but still not happy. So went to Voyd with SME IV, then Jelco TK850M 10" arm, as good as SME IV imo, this set up IMO was as good as what I had before but more involving. Finally moved to Pro-Ject Signature 10, if I could have afforded it I would have gone for a 12, very nice TT lots of detail, depth and blackness, great sound stage. The move to my current TT was definitely a VFM move resulting a great pleasurable listen IMHO.
If I had the money I would possibly go for a direct drive, something like a Brinkman Bardo and tonearm or STST Modus II with probably a Reed 12" or similar arm, or possibly stick with belt and go for an Origin Live Sovereign TT and 12" Arm. Spending much more than what the aforementioned are and I think it can become a bit of a minefield as to whether the improvement is really worth the extra, and its very easily to spend very large sums and end up with something you are not happy with and tricky to sell on with out serious loss.
If I did any of the above would it be a big improvement, I doubt it, perhaps subtle improvements in detail and depth, but it would cost at least twice what I have for maybe a subtle 2-3% improvement so perhaps not worth it.