XFCE has a little task manager application. It's not top or prstat, but it's reasonably lightweight and integrated.
(It also allows you to click on a column heading to sort. That's one of the things that JProc does as well and that you take for granted in a graphical application.)
The original task manager was linux-specific, and the way it wandered through /proc was never going to work on Solaris. But it was easy enough to produce a Solaris version that seems to work well enough for me. Source here.