You didn't say if you wanted to buy one pre-built or if you wanted to build one yourself. I recommend building one. I haven't done it myself, waiting until next year. I hear it's something that just seems immensely complicated before you do it, but after you realize it wasn't so difficult. It's also cheaper than getting one pre-built.
Here's a couple links if you are interested in building it yourself.
A recent post on MMO-Champion with builds of varying prices.
The Build A PC subreddit. Don't forget to check out the Beginners Guide, Resources and Related sections on the right side.