Cast style pistons can sustain upto 400hp under certain situations. If your goal is to race or even just do some street racing or maybe add a nitrous kit then the forged would be a way to go. The cost is alot more, but most kits come with pistons, rings and rod bearings. They usually start at around $400.
As for upping the compression for increased hp this is possible but remember while you have the head off you mine as well wip out that dremel tool and start doing some port work on both intake and exhaust. With the increased compression to optimize your piston swap the head should be worked over, or you really won't notice the change. It really isn't feasable to call this an easy job because you can't really do this with the block in the car. It would have to come out. Figure one day to take out, one day to tear down, half a day reworking the heads, another full day reassembling and so on. I could take up to a week to finish the project. With air tools this would decrease dramatically. Plus take into account that either you or a buddy between the two of you have all the tools to do the job. Pullers, pulley installers, torque wrench, and all the other stuff. But don't let this hold you back to much, if you want it you will find a way to do it...