I like Etys for this: just beautiful for classical music. I own most of their models, and here's how I see them stacking up:
ER-6i: a very good default choice. Very sensitive so you won't need an amp. Uses a very common sleeve size (same as the ER-4 and most Shures), so there are lots of sleeve/fit choices available, both from Etymotic and from other makers (e.g., Comply tips). Has a little bit of boost in the bass, but not enough to really mess up classical music. (It's only a little bit wrong, not drastically wrong.)
ER-6: this is what I used unamped. Its sound is simply clearer and more accurate than the ER-6i's, and according to Etymotic it measures more neutral (sounds more neutral to me too). However it is less sensitive than the ER-6i, and with some classical music you might find that the pianissimo sections can't be turned up loud enough without an amp for fully enjoyable listening. (It all depends, of course, on the music and the listener, so I can't really give you a real thumbs-up or thumbs-down.) It also has an unusual sleeve size and therefore a much smaller selection of sleeve/fit choices (its biflange sleeve, however, fits me ideally so I'm delighted with it).
ER-4P: a really terrific transducer, and pretty sensitive, but its frequency response is tipped toward the bass and away from the treble instead of being relatively flat. This bothers me a lot, giving me an almost physically itchy lemme-at-the-tone-controls feeling within a few minutes of putting them on, but I am in the minority and virtually everyone else seems to like the sound just fine. For me, the best thing about the ER-4P is that you can turn it into an ER-4S with just an add-on cable.
ER-4S: utterly fantastic, but not very sensitive. You can play it unamped from an iPod, but the volume control will be pretty near the top of the range, so those pianissimo sections will be pretty soft.
On the whole I think the ER-6i is a very good choice. And it's a very reasonably priced starter IEM. If he wants to move up from there, he may want to do his own research and figure out what suits him best.
On the subject of amps, although I understand that price is not the only issue, since you specifically mentioned the SR-71 and its price I want to assure you that there are very fine amps available considerably below the SR-71's price point. In fact I used to own an SR-71 but have since replaced it with a $100 amp that I genuinely prefer with my ER-4S's. Although the SR-71 is rightly considered an excellent-sounding premium product, IMO its price is not really correlated with pure sonic performance with these IEMs and with certain sonic tastes.