For the first time since I have owned the 990, ( purchased 1/30/07 ) I tried to connect my headphones to the 990's headhone jack. The 990 is not recognizing the connection, music is still being channeled to the speakers.
Whats up ?

The only reason I plugged my headphones in was to see if my Sennheisser hd 280 pro's sound better than they do connected to my computer. I would love a set of headphones that sound somewhat like my Monitor Audio GR-20's speakers. Thinking I might get better sound from my 990 and, expouse some weaknessin in my computers ability to deliever is my quest for now. I plan on upgeradding my headphones, but it may also be a issue with my computer.
I am budgeted , I need to know how much upgradding I need, and if it will be enough for my computter to deliever.

Hold down the mute button for several seconds. This will enable the headphone jack and mute the pre-amp outputs. And don't forget to repeat the process when you're done.

That did the trick. I couldn't find my owners manual, so thanks for helping out. My computer is incapable of making the Hd280's come to life like the 990. If the 990 is a 10, my computer is a 2
Now to find solutions to bringing my computer up to a level that justifies the addition of another set of headphones.
Any suggestions ?

Google.

With a quick search I found M-audio, which I have never heard of, and ASUS. I don't have any ASUS sound cards although I have had ASUS mobo's and have really liked them.

Do your homework. Make sure the card supports both your hardware and operating system. e.g. this thing requires PCI Express and Vista or XP with no mention of Windows 7.

I have done a few days of research.
As always, trying to keep the price down, so as to buy a nice set of headphones for apx $200 .
The two products which are withing my budget are the " Nuforce Icon uDac 2" ($130) and the " Fiio E7 USB Dac.( $94 ) Both are external sound cards.The Nuforce has nore choices for outputs, ie, RCA jack , Digital Coaxial and headphone jacks, the Fiio E7 has only a headphone jack.

I spent days on Head-Fi.org reading to get to this point. From reading post over there I found out I have one of the worst sound cards in my PC, a Realtek.
Either unit above should do wonders for my PC / headphone listening experence.