Within the Senneheiser family, the PX200-ii is a nice little headphone. Not as super comfortable as the 238, but tighter/more defined sound and much improved isolation, and better portability.
The A700 does have good soundstage (as does all the full sized art AT series) and can be driven easily. You will find that it will have a more pronounced midrange compared to the 238, and a feel of resonance which helps create the large soundstage (at times I feel it's a bit echo-y). The A700 is quite big though; a lot of people who consider the AT headphones don't really consider how big these things are.
Also to consider: M50, Shure 440 or 550, Denon D1001 (if you can find it), Creative Aurvana Live
I usually recommend an Ultrasone or the Phiaton MS300 when people look for a closed Grado.
You might also consider the Symphones Magnum upgrade for your MS2 which I think is around your budget.
My rankings... (best to worst)
comfort: HD598, DT990/770 pro, T50p, HD25-1-ii (I am not fond of hight clamp with earpads, which is why the HD25 ranks low for me here)
sound: HD598, HD25 tied T50p, DT770, DT990
I prefer the sound of the 840, but comfort is hit or miss. The bass and midrange of the 840 is cleaner and has a deeper feel to it. The Ultrasone though has a more viceral bass impact.