To clarify I have the 5.1 ASUS Xonar DG sound card currently with inbuilt amp. 

This is the card I currently have: http://www.amazon.co.uk/ASUS-Xonar-PCI-Audio-Card/dp/B003ZXDOL6 Is it worth getting a more powerful amp for this?

Hey I'm a newbie when it comes to this stuff. Looking for a desktop amp around the £40-60 region with really good bass. My headset is 150 ohm. I currently have an asus xonar 5.1 sound card with build in amp. Looking for a more powerful amp. Thanks