JVA5th, I wanted to let you know that I transitioned from the AT Pro to the XP Deus a little over two years ago. To be perfectly honest with you; I did not like the XP Deus at all when I first started using it. I found the machine to be very loud and "flat" sounding when compared to the AT Pro.
Here's the deal though... I made the mistake of diving into custom programs way too fast. Naturally, the site and desired target type will determine what settings you use. Having said that, if your site allows for it; I would highly recommend that you start off by using Deus Fast with factory settings. Take your time and dig everything!
This is the approach that I took, and it paid off big time. I did eventually decide that I preferred setting audio response to 3, I am a coin shooter and found that this helped me to identify a coin vs. modern trash. I also eventually set my tone breaks and their respective tones (pitches) based on my individual preferences. To date, I still use Deus Fast for all of my base programs and I only make changes sparingly.
I would definitely pickup Andy Sabisch's book, and be sure to checkout Calabash Digger's YouTube videos. Gary Blackwell from the UK also has very informative videos, but you need to be cautious with regards to his custom programs as they were designed for use in the UK.
Don't forget; that the Deus is fully customizable. You can actually configure the Deus to sound and behave similar to your AT Pro. In fact, I made a custom program on my Deus that does just that!
Like I said, start with Deus Fast, buy Andy's book, and above and beyond all; enjoy yourself!