Have you tried http://www.magix.com/int/free-download/ ? I've got the premium edition and, though I've not had the opportunity to test fully, it seems to offer a lot over previous versions.
No, it will not replace MEP Premium 18. MEP 2013 installs in its own directory(s) and creates its own registry files so there should be no proble whatsoever. I am just now installing the trial and will give you my thoughts once I have had a chance to use it.
If you download the trial, during the installation process you will be given the opportunity to download a small utility called "simplicheck" if you already have a PC performance check and repair tool on your system and it works well, you may want to pass on it. It is a pretty good tool at identifying system and registry related problems, but after it finds everything that is wrong with your system, when you click "fix problems, it will take you to the Magix web site to buy the product that will actually fix the problems identified. Also unselect the Magix/Ask Tool bar during installation unless you want it. The free toolbars offered with many free trials are just a pain to get rid of when they change your home page, default search engine, etc.
I have been using MEP for a few hours now, and I must say I am not very impressed. Maybe it is just my PC, but I see virtually no performance improvement, in fact for some things such as video stabilization it actually runs much slower. So far nothing that makes me want to rush out and upgrade.
I will keep posting updates as I work with it more.
George
My system specs are
Should be more than enough to run this app with no problems. Yes, registry is clean and defragmented today as is hard drive (prior to downloading MEP 2013) no apps running in the background except 1 or 2 widgets which always run when I use MEP 18.