Thank you for your feedback. I'm fairly new to understanding this sort of thing, so I appreciate your advice. I have read a good bit of the forums over the last few weeks though, and I didn't find something definitive on if/why an AMP increases SQ.
I don't have a background in music, so I don't think my ear would be very critical.
I did wonder if an amp will only increase volume, or did it add anything else. 2 posts say it will add something else, and one says it may only increase volume.
Below are some more details on what I use at the moment.
My laptop has a SigmaTel C-Major Audio chipset. Here is a rightmark result for a SigmaTel C-Major audio chipset
When I use sr-60 with my laptop HP out I'd have volume at maybe 20%. The only "issue" I can point out is a constant static/hiss. Very obvious when the audio volume is low or zero. I'm hoping the higher impedance of the hd650s will eliminate the hiss.
When I use a Harmon Kardon AVR45RdS Marantz+Speakers with my hp out. I have volume on laptop 100%, and I don't hear any issues with sound delivered from speakers.