Will I hear improvment with an HRT Music Streamer II

Different people will probably hear different improvements because they had different sound cards to start out.  Coming from the intel-HD audio in my iMac, the most noticeable improvement I hear is a considerably more efficient external amp and absolutely no sound coming from the computer or not having my songs randomly skip from computer interference. .  As for the actual sound, I personally found very little improvement.  

I personally love my musicstreamer 2. Im not sure about how huge of a difference it will be with your soundcard but it absolutely blew my onboard out of the water (obviously).  Also, that the hrt improved the sound quality of my headphones a lot more than my amp (little dot mk3) did.  I got it used for about 150 and it was worth every penny. Hope this helps.

I also just got my HRT streamer 2 this week. Using it with my Littel Dot 3  and a toshiba laptop.  There defenitely is a good change to my listening. I am sure that there are more wonderful dacs out there but for my modest system, this is GOOD...VERY GOOD.  BTW, this is just using standard USB printer cable and radio shack rca's and I'm happy.

I have had the HRT MS II for a while now and just recently got the HRT MS II+ and can say that there is a noticeable difference. Most notably is a lot more detail but just as musical, with a slightly larger soundstage that's a little more controlled. It its quite a big difference to my ears and worth the extra money.

anyone tried to pair it with the matrix m-stage amp? that's the rig I'm leaning toward....

Not the M-Stage, but I'm very happy with the results with my E9 and that is one awfully cheap amp. Sure, there are potential problems with the output impedance on the E9, but the MSII hasnt missed a beat. Highly recommended.

E9 seems like a great amp indeed! will check on it

Look for confirmation elsewhere, but IIRC the HRT Music Streamer 2 has an output of 2.25V rms full scale.  FiiO E9 clips with inputs higher than 2.1V, so be careful!  This means you would just have to set the volume down slightly, as a digital 0 dBFS level would run the E9 into clipping.