"How far up the chain do I have to go to get sound that is equal or better than my Aurender?"
No one can answer that question. Sound quality is subjective. There's just way too many variables to give an accurate response. You have to listen to it.
I would give The Cable Company a call. They should be able to send you a few to demo. You can also experiment with equipment you already own, like a CD or DVD player. If they have a digital out, as most do, try them. It should give you some idea as what to expect.
There's another solution you may want to consider. Take whatever you have for a budget, and buy a less expensive transport. Use the rest to buy a re-clocker. Those can make a nice difference especially if you are using different brands for your transport and dac.