Sorry to rain on your parade, but all onboard sound solutions use essentially the same two or three chips, like the realtek al650 (very popular), or the cmedia cmi 8338 (maybe a variant like the 9739, they make a lot of chips).
The main overriding purpose of the "gameports" that you will find on the motherboards (on those few that still have them, USB is king now) is to get a joystick working, not a keyboard. The onboard sound is there primarily for "gamers", not musicians, and are noted for their generally poor performance.
Because most motherboards tend to use the same chips, they are going to be wired the same from board to board, and manufacturers will tend to provide the driver that the chip maker provides. So if you are having problems with your keyboard now, and you find and use another board with the same chip, chances are extremely good that you will have the same problem. I see that your board uses the al650, which most of the new motherboards use. So your choices are going to be limited to those with the cmedia chips. Looking in the newsgroups I see that a couple of people are having midi problems with the cmedia chips also. Looking at cmedia's driver release notes for their older chips they had problems with midi keyboard "hangs".
Asus came out with the p4pe that has the analog devices "soundmax" audio solution, that is supposed to be a "high end" audio solution. But the're alot of reports in the newsgroups of this onboard sound solution not working and noisy sound. Users have had to install a soundcard just to get their sound working right.
I too wanted to find a motherboard with a "decent" onboard sound solution, but I found myself limited to a couple of boards that had good sound, but poor cpu performance, or was very limited with other features I wanted. When the day was done it just didn't make sense to have onboard sound as the deciding factor of a motherboard purchase.
I know that it seems a gyp to buy a board and not have the midi working, but the fact is onboard sound solutions can not be trusted to provide high performance, and that goes for the midi too. Thems just the facts. It makes much more sense to buy a soundcard that has been for sale for a while (like the santa cruz or soundblaster live) because the product is mature and most of the driver bugs have been worked out.
So you can dink around with the onboard gameport all day with some motherboad trying to get the midi working and still not have it working when you are done, or you can plop in a
$30 SBLive and be done with it. How much is your time worth???