New to an amp.

o/

Currently I own a pair of some getting older ath-a700's. The earpads are 95% worn at this point and have almost none of the fake pleather stuff left on them. I'm looking at upgrading my sound a bit.

I don't want to spend all the $$$ right at the moment so let's say i have a budget just beyond $300 if necessary, although I would like to keep it lower.

1. Is it very likely that I will hear a significant change in quality by acquiring an amp over my current 90$ PC sound card?

2. What would be a good pair of headphones to upgrade too beyond these a700's (I listen to a wide variety of music)

Taking my budget into consideration, what would you do? Go for a new set of headphones that will work acceptably until I can buy and amp for like 150-300 dollars? Or buy the amp now and headphones later on?

At the moment I am considering the HD650's and the Schiit Asgard, but would really like some input from a few more experienced people.

I looked around for a rules thread but did not see one right away so forgive the triple post. I'm rather eager to put out the order for some new gear so, yeah.