Dieselboy

So I splurged a couple months ago and bought a pair of Sennheiser 650's. I absolutely love them...and they sound amazing all by themselves.

The reason I'm posting is this:

Before I bought these phones, I did alot of research online and read pretty much every review on them I could find. Quite a few of the reviews said a headphone amp is "a must" if you're gonna use these, because the nominal Impedance is 300 ohms. I'm only using these to listen on my computer though, so thats not exactly a weak power source I don't think.

Some other reviews suggested that a headphone amp will make music sound more crisp, and do cool sounding **** like "back up the soundstage". I got the impression that this was just audiophile BS though.
I'm pretty sure that if you are powering your headphones properly, thats all an amp is REALLY needed for right? Like I said...I'm on my computer here , not trying to listen to these through a walkman or something.

So yeah, does anyone have an honest non-audiophile opinion or comment on this, or even used an amp for high end headphones? I'd rather not spend the extra money if I don't have to. I've heard that after the headphones/speakers are upgraded, everything else you buy such as amps, chords, etc. suffer pretty bad diminishing returns for what you pay for them. If the diffrence is significant though, I'd probably end up buying one.

Thx for any help