No. Keeping memory "clean" is generally not necessary (though that doesn't mean one should waste it).
In its strictest sense, keeping memory "clean" may even be a very ill-advised idea. Although there exist so-called "memory optimizer" software where you pay for a program that keeps your memory "free" by purging filesystem caches, unloading DLLs, and trimming working sets, this kind of thing is snake oil.
RAM is meant to be used, if you keep RAM free, then you could as well have spent less money and bought less of it. In every modern operating system, memory pages that come from mappings are transparently migrated to and from the filesystem cache, which is not only much faster but also avoids disk activity. A disk typically consumes about twice as much power when active as compared to being idle. Your RAM consumes the same power either way (in theory, unused memory banks or unused memory modules could be powered down, but in practice this does not happen -- it would be most troublesome if one tried, insofar as physical memory is allocated and released in a pseudorandom way, so finding a complete module that's unused would be a daunting endeavor).
Bringing a program that is already running to the front is obviously faster and more power efficient than loading its image from disk, loading shared libraries, fixing imports, relocating, and starting up. Likewise, pulling a document out of the cache is faster and more power efficient than loading it from disk.
As long as you don't plug in additional memory (which you aren't going to do, since you mentioned you already have "enough"), the power consumption will remain the same.
That said, running lots of programs that serve no particular purpose (not programs that you actually use, or vital system components) is useless, and needlessly takes away RAM that the computer could otherwise use in a meaningful way (for programs or buffers). There is still a difference between keeping RAM used and wasting RAM.
For example, running 10 instances of Google updater, Logitech updater, Adobe updater, Office Speed Loader, Adobe Speed Launcher and so on, all of which do nothing truly useful, will take away memory that the OS could otherwise utilize as filesystem cache. While these programs may get paged out in presence of application need, this doesn't happen in favor of cache, and in any case it means needless writes to the swap file, even more so as they'll still have the occasional context switch despite "zero CPU", which would mean a page fault every time.
Thus, feel free to throw away stuff which isn't vital for the system's operation and which doesn't provide anything useful that you want. But don't blindly toss stuff just for ideology.