I did a quick google search “connexx 6 download” and found several possible downloads. You do need the Connexx 6 version of the software for xcel. You should be able to download the software without cost.
For fitting hardware, you will need a Hi-pro or similar hardware interface device, two cs-44 programming cables, and the correct programming adapters for your hearing aids. You could expect to expend a minimum of $300.00 to $400.00 to acquire the hardware, depending on your patience in looking for items on ebay, and whether you are willing to use the older serial port version of the hi-pro. With more recent equipment, expect to spend a little more.
Hope the information helps, and good luck with your searches.