G'day Bob.
One of the reasons I bought the Ace, was because you can attach the Sunray probe to it. Prior to buying the Ace, I had found that I had become dependant on using a Pocket UniProbe with my detector (as it didn't pinpoint very well. For a while after buying the Ace, I continued to use it, but decided to learn to trust the Ace's pinpointing ability. Once you learn to pinpoint with it, you will probably feel confident enough it alone. that's one of the key reasons that I like the Ace so much. I understand why you would like to use the extra help, as it's good if you can reduce some of those learning frustrations. Try the Ace without a probe for a couple of hunts and see how you go. There has been a lot of posts in the last month or so as to how to pinpoint using the Ace, so read up on them to educate yourself.
If you are still keen on buying the probe, then I would consider it to be money well spent, as they are a good product. Unlike any other probe, the Sunray is hooked into your detector, and the probe basically becomes a 1 inch coil and behaves just as a coil would when you pass it over a target. It can detect a target 3+ inches away.It plugs into your detector and therefore requires no extra batteries.
If you want to find out more about them, then take up Bill's suggestion, and pop over to the Sunray forum and ask away there as well.
Mick Evans.