Depends what you need it for, viewing distance and room type.
That LCD isn't the LA40D550 unfortunately (usually R4,999 - R5,500), it's the xxD501 or 502 or similar. It's the most basic 5 Series model. Only 1 x HDMI and no USB media player that can play HD movies, unlike the D550 LCD and D450 plasma. If you're sitting <2m from the TV, have 1080p/i content to watch, need to use it as a PC screen to work on, have a bright room and/or direct sunlight, then you'd want to consider it.
Plasma has 2 HDMI ports and the USB HD media player, handles normal TV channels and avi/divx rips (SD media) excellently, great for HD media/HD DSTV when you're sitting >2m back despite lower resolution, suits darker rooms/darker viewing times/curtained rooms due to screen reflectivity. It will beat the LCD at picture quality in rooms with dimmer ambient lighting. Not good for bright rooms and PC work (gaming/media is fine).
If you're considering the LCD, rather put in R500 - R1,000 if possible for the non diluted LA40D550 model.