I tend to agree with @mijostyn that you will have a hard time improving on the JC-3 at this price level, especially if balanced operation is required.
The Boulder 1008 would be a major step up, which I've compared head-to-head with the JC-3. Retail it's outside of your budget, but you might try and find one on the used market for around 6k.
You can also consider Boulder's new 508, which apparently comes pretty close to the 1008 and retails for around 6k. However, it doesn't offer any flexibility with a fixed output at 66dB and a fixed 100 ohm load impedance. While these settings work well for most low out, low impedance MC cartridges, it may not suit your requirements.
The Boulder 1008 would be a major step up, which I've compared head-to-head with the JC-3. Retail it's outside of your budget, but you might try and find one on the used market for around 6k.
You can also consider Boulder's new 508, which apparently comes pretty close to the 1008 and retails for around 6k. However, it doesn't offer any flexibility with a fixed output at 66dB and a fixed 100 ohm load impedance. While these settings work well for most low out, low impedance MC cartridges, it may not suit your requirements.