In terms of modding MS1 is very versatile.
I think it comes stock with Comfie Pads, which have no soundstage but create a very smooth, warm sound (and as the name suggests - are very comfie!).
You can put bowls on them to create more airyness and better separation, with a little sound stage too (but not much). Some people find them so uncomfortable they can't bear them though.
You can go old school with Tood The Vynl Junkie Flats - to create an extremely bassy, vibrant, high octane sound with the least soundstage and separation of all the methods, but still one of my favourites.
You can get sound stage from Grados using Jumbo Pads, which are super comfortable as well. MS1 can be modded to take them in one of two ways.
The MS1000 mod gives MS1 more soundstage than every phones I've ever heard bar the K70*. It requires buying distancers, which several headfiers will make for you at a very reasonable price. In then requires "tuning" with layers of kitchen felt to kill the treble brightness the mod produces.
The cheaper and more elegent (distancers look stupid) solution is unreversable - there is a thin layer of material covering the holes between the sound chamber and the driver - punch through those holes and let the bass through! You'll also need to line the inside of the air chamber with felt to dampen the sound a bit after. Then you can put on Jumbos without distancers and it sounds great. Less sound stage than MS1000 mod, but better clarity. I have this done to mine and I love it, although they are now too bassy to wear flats, so be warned!
In terms of M50 modding -
You can cover over the vents above and below the baffle with masking tape or electrical tape (masking tape having less effect, electrical more) - the moe holes you cover the less bass there will be and the more prominent the mids will be.
You can switch to DT250 velour pads for a huge increase in bass (waaay too much to sound good at first - and most of it in the muddy mid-bass area). To control that bass down to close to stock (but still boosted) levels, get rid of the foam and use pantyhose/tights as a filter and cover at least three the vents on each set with electrical tape.