I added a $30 Xonar card to my upright cab and can hear the difference.
It's even running at a lower sample rate than I was running the onboard sound.
The music is just more detailed and the high end sounds spacious instead of capped.
I knew how I wanted the cab to sound and just couldn't get it there with the onboard audio no matter what adjustments I made outside the PC.
It's pretty close now, but the cheap mylar tweeters in it are too directional and could be slightly smoother.
(the highs are brighter when seated on a stool vs standing)
I might replace them with silk domes if some that will fit turn up cheap on parts express.
Oddly enough, I'm not as picky with the driving cabs since they don't have as many orchestrated soundtracks as newer shmups. (Outrun 2006, but that's about it)
I do still like my speakers at ear level, but not sure I can make that happen with the design I'm heading towards.
One think to note... is that the car based Aura Bass shakers.. I believe they are 4ohm. If you run them with an 8ohm amp.. it can eventually kill the amp. To run them with 8ohms... run two of them, and wire them appropriately. I cant recall off the top of my head, whether its parallel of series, to create 8ohm. If you get it wrong, it will drop it to 2ohm.. making it even worse for the amp.
Running them in series (+ from amp to + of first speaker, then - of that speaker to the + of the next speaker, then - of that terminal back to the - on the amp) will result in an 8 ohm load, at least with two 4 ohm speakers.
Running them in parallel, from + of amp to + of both speakers and from - of amp to - of both speakers will drop it to two ohm.
Basically, the amp can only handle so much current coming back into it.
If you give it two channels to flow through instead of one, a lot more is flowing back in.
The lower the resistance, the closer to a dead short (0 ohm) you are getting.