I have suggested the Toshiba / Aurex SR-510 on this forum in the past and got a bit of grief for the suggestion being made.
I own this model along with other Japanese Vintage Models.
I am not a fan of the Base of the Bearing Housing, it will need a little extra thought and design put in place to enable the Bearing Modifications I like to see utilised put in place.
I have listened to one for a short period and have no concerns for the performance, it has shown another model that is well sought after to be wanting, and as a base model, has great potential. This is one I look forward to becoming a completed modification project, in my view, when complete, it will seriously hold its own against the most sought after standard versions, or even modified versions of DD TT's from the same era of production.
I learnt of this TT through a member of another forum, and one who is possibly the most experienced of Vintage through to Hi End Modern Vinyl Replay equipment that I know. Their assessment of it in use, claims it has a presentation that is closely related to Micro Seiki DD TT's.
The SR-510 proved to be worthy for them to set it up with a Tonearm and Cart' with a Value of approx' £6000. This is the type of investment the user thought was able to be added to the TT and not be wasteful.
I know this TT was used without too much TLC added to the old mechanics, and the impression in this condition was reported on as being very good. My investigation of the mechanics of this TT has shown that a lot can be achieved by doing a little, but the ideal upgrade is presented with a few hurdles to be gotten over.
It is seriously worth a Punt. What is an absolute reassurance for the OP is that the experience of this TT will not set them back anywhere near the $4K being proposed as a spend limit.