warrenh,
You might want to start with something relatively inexpensive just to dip you toe in the water and see if you like the experience. If you're going to spend thousands, I would highly recommend you purchase from a dealer or on-line retailer that offers a money back audition period.
Schiit Audio offers DACs ranging from $99 - $2399 and have a 15 day money back trial period. Benchmark, Berkeley, Mytek and Lampizator make well regarded DACs at higher prices. There are many more. Take a look at the pages of ads in the Digital Category under the DA Converter section. That should keep you busy for a while!
I would suggest you read some reviews, check the forums here, and at Computer Audiophile and start creating a short list of DACs that interest you.
Ask questions. I wouldn't spend any money until you are comfortable that you understand what you need.