Noob Looking to get the most out of sr225is

Heya guys.

I've got a pair of Grado sr225i headphones.  I started with the sr60is a year ago and upgraded within the past few months.  Thing is,  I know i'm not getting my my money's worth out of them because i don't have a halfway decent source.  As i mentioned before,  i'm a noob in every sense of the word.  I'm trying to get my bearings because,  while i know when something sounds good,  and can appreciate it,  i have a hard time getting there (especially where cost is concerned.) While I have been listening to 3.5mm headphones my whole life I have had a few rare opportunities to listen to really good setups from pros. So basically I'm trying to figure out how to go from using my sr225is in what I assume is a completely disgraceful way (3.5mm converter on them) to getting the best out of them.

I'm defiantly building up rather than diving all in for various reasons (mostly cost) so what i'm looking to get a sound-card that can get the highest quality sound out of my 225is (it don't have to exceed them though I don't mind it for when I upgrade the headphones someday) and I need to know what kind of cables / adapters (if any) I’m going to need. Expect newbie followup questions. xD

I have $300 to spend max.

Thanks guys,

-LittleWolf

that would overshoot my $300 budget by about $300.  o.o

I'm a highschool student.  I don't make much.  Is it really not worth doing anything at all until i can afford that?

I've been watching ebay for a few days and the grado rs1s are going for almost twice as much as they cost new.  >..>

The rs2is however seem to be a bit more along that price range.  Thoughts on this?

Also what is the quality difference like with the 0404 and Fiio's e7?  I had an E7 a little while ago (but not the e9) and managed to break it (usb port pushed into the box,  opened it and looked inside,  was unsalvageable) i was always very gentle with it so that had me a bit irked.

What i was really looking to do was get a decent soundcard now because i haven't really even had a chance to use the sr225is at their potential.  I figured i could handle the soundcard now and upgrade the headphones as the next purchase instead of trying to get it all at once and making compromises on either side.

I guess i have future proofing in mind,  so can anyone tell me where i can learn more about what i can learn more about what is required to drive any given headphones?