You should do some more research on the T50RP mods, and the results people have gotten compared to the Mad Dog.
Sure - you could TRY doing it yourself and save some money, there are a lot of guidelines & instructions out there, but Mr. Speakers has their own "secret sauce" (process) which, may be the best method of modding them, or at least better than the DIY methods. That's all up for debate, but at least w/ the Mad Dogs there's no risk involved, you know you will get a finished product that is well reviewed and praised for their sound + comfort. Also keep in mind they come with the very comfy Alpha Pads which retail for $59, which will also work on a variety of other headphones. And lastly, once you have the Mad Dogs, you can upgrade them to the Alpha's at a reduced price.
So, of course you could go it your own, but if you don't know what you're doing there's no guarantee you'll even improve them, let alone get to the level that the Mad Dogs are at. It's up to you if its worth the extra price or not.