You could also start with Cakewalk Express, ( also about 30 dollars and sometimes included with hardware as "bundled software" as well ).

CW express has excelent midi editing features. It may ( or may not ) be limited in audio features vs Power Tracks, but I'm not 100 % sure on this because when I had Express I always used N track studio for multitrack audio ( actually I still do and I prefer it over Sonar for strictly working with audio.. great bang for the buck program )

If you want to spend a little more, but not the price of Sonar, CW Home studio will give you good bang for the buck too.

I would suggest a look at the Shareware music machine at http://www.hitsquad.com/smm/?pr2 . Here you can find many trial and shareware downloads that you can try out to see what works for you. There are even a few pretty decent freeware apps that might surprise you. ( Quartz studio freeware from Digital Sound Planet does a pretty good job of midi editing and allows for 4 tracks of audio recording ).

AJ