Anyways, mixing RPM's and DEB's on the same install seems like a good way to hose your box to me
Even with alien (converts rpm->deb->tar.gz->etc) it doesn't work well because RPMs don't have as much packaging information as .debs do, which is one reason why APT works so well on Debian, then you have version number differences, etc. If you run Debian and can't find a .deb for your software (there's nearly 9000 packages on Debian's repository, you should be able to find something comparable in there =)) then compiling from source is usually the safest bet.
Even with alien (converts rpm->deb->tar.gz->etc) it doesn't work well because RPMs don't have as much packaging information as .debs do, which is one reason why APT works so well on Debian, then you have version number differences, etc. If you run Debian and can't find a .deb for your software (there's nearly 9000 packages on Debian's repository, you should be able to find something comparable in there =)) then compiling from source is usually the safest bet.