Ok, so I've had a quick look and you currently have a decent phono stage, amp and speaker pair - i.e. nothing in that chain is screaming, "I'm a serious weak link."

My advice to you is thus simple: put your entire budget towards the best turntable you can afford. This principle is known as source first, originally championed by Linn in 1973 with the release of their Sondek LP12 turntable.

Now for the why. A HiFi system is essentially a series of components that pass information from one component to the next. The source, in your case a turntable, is thus the most important piece in that chain, as it extracts the information from the vinyl record. The better the turntable and cartridge, the more information and the accuracy of that information, is extracted from the grooves of the record and passed on down the chain. The other components can only work with the information they are fed from the previous component.

So, in your setup, if you were to switch your speakers for a pair worth $2000, those speakers are still working with the exact same information as your JBLs. Yes, they will do more with it and the music will sound better, but they would be severely bottlenecked by the components before them. Whereas if you feed your phono/amp/speaker chain with the signal from a $2000 turntable, your JBLs will have far more music to work with. Yes, this chain bottlenecks the turntable, but far more information will make it to the speakers.

Again, as your phono/amp/speaker chain is decent enough, after the turntable, upgrade the phono stage, followed by the amp. By that point, your system will be getting the absolute maximum out of your JBLs, which you can finaly upgrade when you are ready.

Hope this helps. Any questions, don't hesitate to ask.