Sampling doesn't destroy quality if you do it properly. When you store everything in WAV format you are digitally keeping all the information in that file. Cutting out and 8 count or 32 beats isn't going to change that. All of the top Cheer Music Producers in the industry know this and work this way, and this is how I was taught long ago.
Yes, you have to render down your project when you are done, that is the only way to do it, however you should be rendering to a WAV not an MP3. WAVs are larger files because they hang onto and contain all information and data in it's fully expanded form.
Starting with WAV format and not changing that format until the very end when you save your mastered copy is the only way to get the best possible sound out of your material.
Working with whole songs in mp3 format in ACID uses up way too much memory, slows things down and is not as precise nor does it give you enough data for the full sound you are looking for.
Sampling is not a waste of time. It requires time spent, but you have to put in the time just like proper EQ'ing, etc, to get a good result. Short cuts usually result in poor quality.
Ask some of the top names in the business.