I've been doing some conversions myself and have found that if I run the noise reduction first and then amplify it brings the volume back up to good hearing level. Also, on old recordings like that I found the High Pass Filter at somewhere between 150 and 300 works great for taking the muffled, cassette sound out and bring it up closer to a new recording feel.
Probably way too late for a reply on this, but I only found this awesome program a week ago. God bless!