Direct upgrade from x-fi xtremegamer for M50s?

You'll probably get more info on sound cards over at the Computer Audio forum.

I personally prefer to have an external DAC/amp rather than a new sound card inside the computer. You get a nice solid device to put on your desk, with a volume knob for analog control. It's easy to take with you and use with a laptop or at the office. And if you upgrade to something else further down the road, it's not hard to sell the old DAC/amp unit to recoup some of the cost.

Since your budget is $200, I suggest also searching for reviews on the Audinst HUD-mx1 and seeing if that suits you.