I would definitely not put an amp on stock speakers IMO. Most stock head units probably put out about 15 watts rms to each speaker channel, and the stock speakers i doubt could handle more than 25 watts rms. If he has the money, def. get some good comps and an amp. A decent set of comps is usually rated at at least 50 watts rms, a lot of them are about 100 watts rms. Running just a head unit, especially if it is stock, is not going to give them more than 20 watts and the comps won't be seeing their full potential. There are plenty of decent comp sets out there for not too much, you could pick up a good pair here on the forum if you just look around. Profile makes very cheap amps but they are quite nice and basically do their rated power. So look for a decent set of comps here on the forum or someone could recommend some for you, and look at maybe a profile amp to run them. If not, i am sure you could find some used amps here that would run them fine.
2004 Honda S2000
Audison Voce AV K6; Rockford Fosgate 400.4
SoundSplinter RL-i8 ported; Kenwood Excelon X500-1