Tony,

The best app for you is the one that best fits your budget and your workflow preferences. Acid pro is an excellent app for recording audio and working with and editing sound loops and samples, but it might not be a very good choice for someeone who is interested in having good midi editing capabilites as well.

There are many good apps out there, ranging from free programs such as Audacity and Krystal, to lower end end commercial offerings, such as Power Tracks Pro ( great value ) or Cakewalk's Music Creator, to higher end, such as Sonar or Cubase, to top flight apps found in big studios such as Pro Tools and Nuendo.

Here is a link from KVR-Audio that lists quite a few of today's popular apps ( as well as some lesser known ones ). Each link gives a general description of the product, plus links to the product's home site.
http://www.kvraudio.com/get.php?mode=results&st=adv&soft=h&type%5B%5D=63&type%5B%5D=60&type%5B%5D=10&f=0&fe=0&mac=1&osx=1&win=1&free=1&com=1&un=1&sf=0&receptor=&sort=1&rpp=100

Good Luck,

AJ