For question 1)
The headphone I DID gift my girlfriend was the Koss KSC 75 clip-on headphones. In her case, isolation wasn't so important, but I bought these because they are comfortable (comfy!), they don't leak much music out (library appropriate), punch WAY above their price for sound quality, and are inexpensive because she tends to trash her things
They have a lifetime replacement policy, but I can buy new ones cheaper than the shipping cost
I honestly prefer them to what I heard from the new Philips offerings I heard at my local electronics store, using my iPod, line-out, and FiiO E5 amp.
For your lovely other, I would wonder about which is more important to her: Soundstage, isolation, or a balance between the two. Obviously you've figured out that IEMs are like earplugs... I believe the Sennheiser model you refer to is a canalbud, which is somewhere between an earbud and true canalphone in that it doesn't insert very deeply into the ear.
If isolation is most important, nothing can beat a canalphone like those from Shure or (my preference) Etymotic. They're like earplugs, and my first high-fidelity headphone was the Etymotic ER*6i that fit far better than the Shures I tested side-by-side at a Macworld Expo, without distorting like the first two models of Shures when I played Kanye West's "Gold Digger" (hate the track, but it's a good test). The Etymotic comes with 3 sizes of silicone eartips, plus expanding foam eartips. Based on my experience, if you actually want to not hear other people talking while studying, IEMs are the only style of headphone that cuts it, and canalphones a work best. I'd recommend the cheapest Etymotic you can find, failing that JVC marshmallows are well received, and Head-Fi'er "Clie-OS" has THE in-depth IEM round-up on Head-Fi. RE0 is another IEM I see a lot of people write about for value.
If soundstage is more important, well... soundstage doesn't expand nearly as well as an open-back headphone. The best sub-$100 (USD) closed-back headphone with a good soundstage I've heard about is the Creative Aurvana Live! (Widely referred to as CAL!) headphone. It's a clone of the very well regarded Denon D1001k, same Fostex driver. It is closed, but doesn't isolate from outside noise very much. Very nice sound, comfortable (for a closed can, as I'm sure you know they all build up heat & sweat after a while), and a great all-round headphone. May be slightly larger than a typical supra-aural (on-ear) headphone, but I'd still say it's portable, doesn't stand out in looks. If you could swing it, this would be my pick.
Another closed headphone that isolates better than the CAL!, so maybe a good balance of priorities, is Sony's MDR-V6. Good price, good sound, good isolation, clamps a little harder than the CAL! which helps with the isolation, a "good" headphone all around. I would describe the looks as "professional" rather than "fashionable," "sleek," or "gangsta." Also, hella durable!
For question 2.)
A more powerful amp fills out the sound... It is noticeable, usually doesn't change the signature of the headphone but makes sounds more distinct and present. Volume <> Amp power. A more powerful amp.... The best way I can describe it is like "An explosion can sound loud, but with a more powerful amp the explosion will sound loud, Big, and Dangerous." With more power, a headphone can more easily produce the long wavelengths of deep bass with authority, but also everything else. If you're at home and you have a receiver for your speakers, try plugging into that as an amp and plug your headphones into the 1/4 headphone jack (turn down the volume first!) to get an idea what more powerful amps can do, although many HTIB and receivers aren't built with the cleanest headphone jacks. Another thing I would mention: my iPod Video's headphone out jack was starting to short out and stuff, and playing my iPod through my car made my speakers sound like they were blown-out. I bought the FiiO L11 line-out dock adapter (LOD), connected that to a FiiO E5, and the effect was like I had bought whole new speakers. IMO, the cheap LODs are a must if you want to connect an iPod to another amp.When buying headphones & components, the difference is headphone>music file quality (bitrate)>amp>DAC. A better DAC may pull more resolution out from high-fidelity files, but most of the time I'd say spend money on a DAC last.
The FiiO E7 is basically an E5 with a DAC added, FiiO intends to update the E7 with the E6's amp section soon. These amps are barely better than what is built-in to an iPod. An E11 is like an upgraded E6, with much more power, but still only an amp. The E17 is like an upgraded E7, with a more powerful amp, "better" DAC, treble/bass equalization. Not quite as powerful an amp as the E11, but still quite good. The E9 or E90K are essentially the same (with a different dock for either E7 or E17), desktop amps that are the most powerful FiiO makes, and basically are a good sample of what a solid-state amp can do.
Tubes are very interesting to me, and since I have a powerful SS amp in the shape of a Yamaha receiver with a more-than-decent headphone section, I'm about to explore what tube/valve amps can do. I like the idea of changing the sound signature by changing a lightbulb
I should get a tube amp based on the Super Simple design within days, I should drop reviews on that, my AKG Q701 headphones, a comparison of amps and Q701 vs AD700, and how it all figures into gaming with surround sound
find them when I write them!Edited by Evshrug - 11/16/12 at 10:07pm