I don't know the differences between Quick Score and Sonar, and you don't say if you're in 32 or 64 bit Windows. But according to the Quick Score site it requires only a few MEGAbytes of RAM, and they don't even mention a CPU recommendation. I'd say SONAR does not need much horsepower, you just got used to a program so light that it only needed a donkey (which doesn't mean it's not a good program). You can't talk about Quick Score and SONAR on the same day, they are of totally different weight.
Your system specs are just a bit over the minimum specs for SONAR. With the minimum specs no software can show it's true power. And it's ASIO drivers made for your M-Audio that you should use, not ASIO4ALL. I have a similar machine as you. I use SONAR 8.5 fluently, when I remember to freeze or bounce the heavier softsynths sometimes. Projects of 30-40 tracks, 50/50 MIDI and audio behave OK.
When you look at signatures here, most folks have i3 CPUs or better. Nobody designs software for
machines as weak as yours and mine anymore.