Amp for Desktop w/ Headphones

[elkibblez]

Alright, so I currently have Sennheiser HD 380 Pros (54 ohm), which I mostly listen to off of my desktop. My desktop is a 4 or 5 year old HP with a 4 or 5 year old sound card. Now my questions are these:

1. Do I even need an amp?
2. I'm looking at Sennheiser 595s (50 ohm), would those need an amp?
3. If not an amp, what else should I look at to possibly improve sound quality so I get the most out of my headphones?

Thanks!

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