Your post is a little hard to understand - are you having trouble installing Sonar or the Tascam? What kind of computer do you have? How much memory? How fast is your hard drive?
If the Tascam has a USB 2 out you should definitely upgrade to a USB 2 port on your computer - USB 1 is just to slow in my opinion, especially for 24 bit audio - but if I am not mistaken the Tascam only supports USB 1, so it won't do you any good to hook it up to a USB 2 port on your PC.
One of the keys to avoiding pops and clicks is adjusting the latency and buffer settings in Sonar and your soundcard's preferences (Sonar < Options < Audio).
- Chris