Well- since it sounds as though you'll be reinstalling then I'm going to suggest that you NOT do apt-get upgrade. So many people do that then hose their system up and can't fix it. It just isn't necessary. I'm not even sure why everyone seems to think it is. Testing and Unstable are named as they are for a reason. I would only suggest upgrading packages if there is something that a more stable version cannot provide. With that said..

Use Synaptic. (Kpackage is OK too) It will show you all the dependencies required, what it's going to remove and what's going to be installed. It works flawlessly for me. I just installed Superkaramba and the only change made to my system was removing Karamba. I'd also suggest not trying to install 100 packages at a time- take your time, get familiar w/ apt-get and what it can and cannot do. If you installed 1 or 2 packages and your system gets hosed it's alot easier to figure out what caused the problem. COnversely, if you installed 150 .debs and your system gets borked what tehn? Those dependency problems can be annoying but they can also be fixed if you learn the intricacies of apt.