You can get a 2080 super for that. You can fit a 2080ti in your budget with the adjustments @5x5 suggested but I still question if the 3900x is worth it for you - you can just save the money.
Also please quote people or we won't get a notification.
Are you sure you need this? You could go for a 3700x and a better graphics card... unless your programs take a long time to compile or are particularly CPU intensive you probably have no use for the extra cores.