Before you try any toys, play around a bit with your fingers. Use a good lube, and see what's up there, where everything is, ans what feels good to press on, rub, etc. Once you do that, you'll know what kind of things you like and can choose a toy that fits. If you put the curve of a toy forward it will tend to stimulate the prostate more - check with your finger to see if you like this sensation (the prostate feels like a bump a couple inches up in the rectum on the front side (towards your belly).
One thing to keep in mind is that the anus and rectum can be sensitive to things in sex toys or lubes- so be prepared to try a couple different options if things don't feel good. If you don't have lube yet, you might want to look for something glycerin free (such as Maximus), or if you have oil-lube-tolerant toys Boy Butter works well, too.
The Power-T looks like it would be a decent starting toy, but you'll probably have to hold it in, and it's going to be stiffer than a silicone or jelly toy, so you'll want to be aware of how hard you're poking it in (I once slightly bruised myself through over-exuberant use of a hard toy).
Bravo on having the courage to try anal stimulation, though, and best of luck!