Are You outside of the United States? I only ask because here the SR80i are $99 and the MS1 are one dollar more at an even $100.
 
I have the SR60i and the SR80i and while I love them both for various reasons I find the SR60i are more forgiving for lower quality mp3s and make just about any kind of music sound great right out of the box.
 
unlike the SR60i the SR80i took quite a long time to burn in (i'd say over 100 hours) at which point any of the initial shrill highs were gone and replaced by a very clear and robust detail,also the 80i have a slight bit more bass the the SR60i.
 
Did you allow for that much burn in time? also with Grado it seems to me the source component is essential to how they respond.I use a Sony NW-F807 and have to say the SR80i sound amazingly warm,rich and highly detailed now that they are burned in,they sound far better on 320kbps mp3s,FLAC,APE and WAV files imo than with lower bitrate files. so if you haven't give them a bit more time,they really are great sounding for the price.
 
I haven't had the opportunity to hear the MS1 or 225i yet.but will be purchasing both in 2014 as I love the Grado sound.and one nice thing about Grado if you do find you don't like them is that they tend to have a better resale value than other brands.
 
one last thing I'll mention is,if you have had your MS1s or SR225i's for longer,try putting the earphone cushions from either of them on the SR80i.because the older cushions are worn in more they will be softer and bring your ears closer to the drivers giving the SR80i much louder volume and more comfort.I only got mine a few months back but the cushions I have on them are over 3 years old and falling apart.just a thought.some people don't like their ears that close to the driver,i do,its just a matter of preference.

The 80i's easily have 100 hours on them, and i bought them 2nd hand. They were my first pair of Grados before i got the MS1's, then recently i got the 225i's.  If anything i'd say the 225i's have had the last amount of use, and will all three cans i used the same L-Cush pads as i much prefer them over the stock flats.  I've never heard the 60i's but the MS1i/225i both have a similar sound, the 225i is just more refined.  The 80i has less mids/lows, and too much high end for me.   I also find the better the set of headphones the more unpleasant low quality source recordings become.
 
Since you already have the 60i/80i i would just go straight for the 225i's.  I can honestly say i will never use the 80i or MS1 again now i have the 225's as they are that much better.

Thanks,that's good to know about the 225i's. they're going to be the next headphone purchase for me.
 
The 80i's definitely have more prominent highs and aren't everyone's cup of tea so to speak,so i get where you're coming from. I ordered mine to hold me over until my 60i's return from the Grado factory (sent them in to be re-cabled after 3.5 years of daily use and abuse).and while I do love the 80i's I am sorely missing the 60i's and can't wait to get them back.
 
I have the L cush pads as well.they are nice and add a lot of detail and a little more sound stage to me.the only thing is they seem to attenuate the over all volume (most likely because my ears are farther from the drivers when using them) I need to break them in more because they do sound great,especially after applying the basshead mod.

What a concise and wonderful review, sir. I like it.

I must say I have had these headphones for near on 10 years and I couldn't disagree with you more regarding the sound signature.
I cannot comment on the amp as while using these I was younger and was ignorant to such things, however if "properly amped", why would it distort? Wouldn't properly amped imply that the amp setup is ideal for the can, thus this makes no sense??
 
In any case I am sorry you feel this way, I had a very different experience with them and they are responsible for my now expensive habit 

I cannot explain it but power them from any kind of decent amp and the bass will start to distort.  They only seem to work with very low power devices like iPods.   There just sound terrible to me, no detail at all, i'm sure if you went back to them now you would cringe.

Well I finally went back to them haha.  I am waiting on some CIEM's and had no other headphones so broke them out of retirement.
Listening to them out of a beyer a200p I think they sound quite fine.  I wouldnt say they sound good compared to other headphones I have had of late, but at low listening volumes (and I must emphasize this) they are very nice indeed.  
When the volume goes up however the enjoyment does diminish steeply lol.
In saying that, for a pair of headphones I bought in my teen's to still be working and sounding respectable I couldn't be happier.