Stock lifters are fine. Springs are the weak link in the valve train and can allow valve float at high rpms. Most people don't spend a lot of time at redline, or don't notice valve float there anyway.
The underdrive pulley slows down all of the accessories driven by the serpentine belt. This reduces their effectiveness slightly, so there is a trade off that anybody should understand before buying an underdrive pulley. The only issues I've ever heard about have been from a couple of guys with tons of electrical add-ons like massive stereo stuff or lots of off road lights. The slower alternator might not put out enough juice for those extreme cases, and those guys might have lights that flicker or something. The other 95% of people never notice any drop off, and with the option of LED lights so common now I bet a few of those guys wouldn't have the same problems today that they did 10 years ago. I've never heard any complaints about problems with the water pump, power steering pump, or AC compressor. Ultimately it's your call though. You've got to be able to sleep at night.