hi viz, not really hi viz
I have a 340PD with the Hi-viz sight. I like the sight, but it really doesnt make a difference in the dark. Its a light gathering sight, but that's just it, it needs light to gather. I would just leave the sights you have on there and pony up for something that CAN work in the dark.
Thats why I strapped on some Crimson Trace laser grips. If any of you are contemplating getting them DONT get the smaller all plastic lg-205 ones. I got them first cause I wanted to keep the gun as small as possible, but I got them and they felt like crap in my hands, and returned them right away and got the rubberized grip ones (lg-305)
I shot some ridiculously tight groups when I got the hang of my laser grips. The only way to go for concealed carry. Here she is