Glad you're liking Kantoix.
KGet and Synaptic are a little different. KGet is a tool for downloading files to your hard drive. Synaptic, although it downloads software from the Net, it actually manages and installs those applications on to your computer. KGet is just a download manager, nothing to do with installation.
The best way I can describe it is, Synaptic keeps your applications in order, as well as all the necessary system libraries required to run those applictions on your PC.
Synaptic (from the default install) is set up to only download applications built to run under your Kanotix/Debian operating system. It' uses a pool (or repository) of applications that are Kanotix/Debian ''approved''. You may notice that not all applications that are available for Linux are listed in the repository... although there are a lot of packages are made available.
When you install an application via Synaptic, it analyses the software you want to install and checks to make sure your system has all of the support applications available. If it doesn't it downloads the appropriate ones that the software you want to install needs to run properly.
Say you want to install the KOffice suite. You do a search inquiry under Synaptic for KOffice then mark it for installation. What will happen is Synaptic will notify you that you require several other applications installed in order for KOffice to work. You just have to approve Synpatic's request to install the support apps, and KOffice then gets installed.
I agree with you, Synaptic is the most useful software installer I've ever used on ANY operating system.
To answer your other question... YES, KGet will work with any other browser. It's not browser dependant.
I like Konquerer simply because of it's integration with other features of KDE (Kmail, KGet, KOffice, etc.). It also allows me to access some websites that Mozilla/Firefox can't access. Those sites that only permit MS-Explorer users can be fooled with Konqueror, as it has a "browser identification" spoofer... making it look like it's a certain brand of web browser.
Sorry for the long post.