Just to chip in a little.. Actually the PK3 has bass as deep (if not deeper) than the PK1, just not as "big", bass extension doesn't goes as wide across the spectrum.
With portable players, yes, the bass sounds like a small tapping stick, has a little impact but sounds very small. However, the Yuin PK3 (not just on bass) will scale very, very well with amplification, and to me, the relative scale of improvement is more than the difference between PK2/1 unamped and amped. Heck, I tend to use my PK1 unamped on my Shuffle, the basic characteristic of the Yuin PK1 is there, just not as refined. The PK3 on the other hand will sound rather different after amping.
Oh and remember to put foams on else they just sound plain weird.
what?, you may consider the MX580 as well, pretty good for the price. I'm not with swbf2cheater on this though, but I do feel the MX580 does have its own good points. In particular the mids which are more lush and easier to listen to (compared to PK3 where the mids may sound just a hint drier). Some people might like the volume control attached on the cable (though I don't), so if you know your friend will love having something with a VC on the cable.. Why not?
