[Nebster173]

B

 

[NA Blur]

Here is what I hear between the two:
 
=2631&graphID[]=373]http://graphs.headphone.com/graphCompare.php?graphType=0&graphID[]=2631&graphID[]=373
 
You gain a tad bit on the 100Hz range which is nice, but the treble can be unbearable at times.  I suggest something like the V-Moda M80 which is going to be a better upgrade than any lower tier Grado.  In fact I have gone all the way up to the RS-1i and still did not like it any better than the 225i I had at the time.
 
For metal you want an excellent and up-front sounding midrange, extended bass, and slightly rolled off highs to prevent any fatigue.
The curve for the Brainwavz M2 for example is almost ideal for metal.
 
http://www.innerfidelity.com/images/BrainwavzM2.pdf
 
The Sennheiser Amperior is another great Metal headphone, but a tad expensive for what you get.  I still would take it over a Grado any day of the week.
 
http://www.innerfidelity.com/images/SennheiserAmperior.pdf
 
The Amperior was a tad bity with most of my music and fatigued my ears after just 10 minutes of general listening.
 
Here are a few suggestions according to sound quality and then budget:
 
1.)  V-Moda M-80 @ $200
http://www.innerfidelity.com/images/VModaM80.pdf
 
2.)  Denon AH-D2000 @ $350 or less
http://www.innerfidelity.com/images/DenonAHD2000B2012.pdf
 
3.)  HiFiMAN HE-500 @ $700 or less
http://www.innerfidelity.com/images/HiFiMANHE500.pdf
 
The V-Moda M-80 is within your budget and I tried to give you some definite upgrades to work toward in the future.  My favorite being the HD-500, but for nearly half its cost the Denon AH-D2000 is an amazing buy.

 

[Fringe]

I had the AD900 and SR225i at the same time and I think the grado was better with hard rock genres. The bass impact was a lot better on the grado and the agressive presentation works better than the airy sound of the AT. I think the difference was pretty big between the two. With the grado you have take into consideration comfort and the possibility of it being a little too harsh. The highs didn't bother me too much but the comfort can get to me after a while.