Hi Taph---
the 280 and 497s are similar inasmuch as they are both pretty neutral sounding. The 280 has deeper bass, better articulation, and a flatter frequency response (i.e. is more neutral). The 280 is also much sturdier, better made, and can be folded up nicely. The 497 has a broader soundstage, but not by much. The 280s also have a more up close sound distance. All in all, I prefer the 280s, but I think you'll likely continue to find a use for both phones.
What I (personally) mean by some of these terms: (other poster definitions may well vary!)
soundstage--placement of instruments/sounds in a two dimensional (x and z axes) imaginary space between your ears. Crappy phones give you right and left (stereo) division. Better phones divide instruments more precisely and give you some illusion of depth as well as width.
articulation---how well instruments/voices are distinguished from each other. Difference from soundstage: soundstage will divide drums and guitars from each other in a positional way, articulation will divide one guitar from another, or even let you hear individual guitar strings being plucked at the higher end.
listening distance---how close you are to the music. Senns traditionally have you a little bit "farther" from the main sound source than Grados. Again, like soundstage a mostly subjective distinction, but as you listen to more phones, the differences become more apparent.
Studio phones---neutral sound and closed design meant for use by sound engineers, intelligent DJs, and the general public. Low impedance (less than 100 Ohms) and sturdy for easy power in the studio and to withstand abuse from users. Dimwit DJs use heavily flavored crap like the Sony V700DJ, which are "warm" i.e. have lots of bass. (The opposite is "bright" which is treble biased. Only in headphone land are warm and bright antonyms!
) Phones can also have a mid range bias as well, but this has no special name, to my knowledge. "Flat" means the frequency response curve resembles a straight line, i.e. has no bias (either emphasis or deficiency) in any of the frequency ranges.
For open phones and an iPod, I think you are already well served by the 497s. Decent bass, good overall balance, and easily driven. You may like Grados; some (like me) think the closer listening distance and aggressive mid range boost make rock very fun to listen to with these phones. Others find the listening distance too aggressive and the sound overly bright and therefore fatiguing. (Yes, phones can have boost in both the mids and high freqs.) Grados are also very easily driven, having a similar impedance to the 497s.
The 60s are probably the most neutral Grados except for the 325s, but the bass is pretty minimal and the trebles not as clear as on other models. The 80s are a bit too bassy (i.e. warm) and this makes mids a bit less emphasized as well. The 125s are (IMO) the best price/value deal in Grado brand, and have great bass, balanced though engaging mids, and a clear detailed treble. Problem is that the treble is maybe a bit too much here, making these the brightest of Grados and fatiguing to some (not me.) The 225s are just sort of there---more $$$ than the 125s, somewhat less bright, but not really worth the extra bucks (IMO) The 325s get the treble balanced again and give you a tad more bass---just about perfect, but also $300.
As you can see, Grados are very quirky in their sound. Many also feel they are uncomfortable (too tight), poorly made, and/or ugly. I disagree to varying degrees on these issues, but will concede that Grados are not for all. If you can listen to em, try them as they may suit you much better than the 497s with your music choices. If you can't audition em though, buying "deaf" is not recommended as you seem to prefer neutrality...
Any other questions, ask away! But I think you will be more than pleased with your 497/280 combo.
