Personally I've never seen one of those mains-powered amplifier aerials give a good signal. Even worse, when I had a close look at one once, I noticed that the magnificent crossbar aerial part wasn't even wired into the 'amplifying' base!! I therefore would strongly suggest (from my own experience of course) that you avoid them like the plague.
The bottomline is, if you get the signal quality you want from the plastic strip aerial, then just keep it... Another idea for you: Wire the aerial socket through a very small (<=1Amp) lighting fuse, and then into the earth of a socket. It should protect the PC from any surges and will enable your entire house (through the mains ring) to become an aerial? Dodgy I know, but I've seen it work wonders.