If you have a fair few cassettes to do, I would suggest that you have a look at buying the Magix Audio Studio or similar. Thing with cassettes is that expectations have improved over the last 20 years and that having s0dded about getting your stuff onto the PC, that it might be worth re mastering it while you have it there.
I use the prog myself occasionally and it allows you to boost the dynamics and loudness, as well as removing the hiss and lots of other options, etc. etc.
Makes my "Smurfs - The anthology" a different proposition altogether.
Conan