Ok, i just found this gem few days ago. It's called SRS Audio Essentials. It's a sound enhancer developed by a famous company SRS Labs which supplies audio enhancing algorithms to various software companies and also hardware companies like Philips, LG, Grundig, Samsung and so on. What's so interesting about SRS Audio Essentials are two things. First is that they offer a limited free version and second that it works for all audio that you playback on your PC. It doesn't matter if it's a music player, video player or a game. It applies sound processing to all sounds. Even windows sounds! So you don't have to bother with plugins that only work in one application but not in the other.
In a nutshell, it works very similar to Creative Labs Crystalizer or Analog Devices (ADI Soundmax) BlackHawk for anyone who has ever used it, except it can be used on any soundcard. And offers much more settings and tweaks.

I have tested it for music on my Altec Lansing MX5021 speakers and it gives very pleasant effect to the sound. The bass feels a bit deeper and smoothed out (sounds softer) which in return makes it feel like it's much stronger than it really is. I've also tested it in NFS Hot Pursuit 2010 and CounterStrike:Source and it worked great as well. Again with deeper bass and noticeably more high and mid frequency details. It didn't ruin the games 3D sound positioning even in Music mode used in limited free version which is a good thing.
It even worked well on my laptop and laptop using headphones though sound "quality" varied based on content used. It sometimes worked better with Speakers setting than with Built-in. But in general, very nice effect on small laptop speakers as well.
Free version is well, free but has certain limitations:- works only for 2.0 or 2.1 speaker configuration
- only Music mode can be used
- only Speakers and Laptop Speakers (Built-in) can be used
- none of the advanced settings can be changed (sliders below)
- Smart Volume cannot be enabled
What might also be interesting is that they sell this thing for end users as well and it's surprisingly cheap. $19,99 (around 15€) for a single PC license. Various software companies sell plugins for Winamp or Windows Media Player that cost the same, but have very limited functionality (you can only use them for that program and not for games either). This one works in ALL applications. So it has a much greater value.
I'll be using free version for a while but i think for the price, it would be well worth it, based on what i've seen with my ears so far.
Give it a try and see how it works for you. It's free, so there's nothing to lose
DOWNLOAD:http://www.srslabs.com/audioessentials/